I built this guide because my routine checker kept telling people what not to mix, and the next question was always “ok, but what does it actually do?” So here’s every active the checker knows about, in plain English.
Each card covers how to use it and what to keep it apart from. The pairings come straight from the same research my checker uses, and the sources are at the bottom.
Brightening and dark spots
Exfoliating acids
Retinoids and anti-ageing
Spots and oil
Hydrating and calming
Protection
Vitamin C
Also called ascorbic acid and its derivatives
Vitamin C is an antioxidant. Day to day, it helps fade dark spots, brightens dull skin and mops up some of the damage UV does. Pure L-ascorbic acid has the most research behind it – but it's also the fussiest: light and air break it down, and it turns orange as it goes off. Derivatives like ascorbyl glucoside or sodium ascorbyl phosphate are gentler and last longer, they just work more slowly.
Mornings, under your sunscreen. One good vitamin C is enough. If pure L-ascorbic acid stings, try a derivative.
Dullness, dark spots and anyone who wants a bit more from their morning sunscreen.
What not to mix with vitamin C
Space them out
Work well together
Fine together
- NiacinamideFine together. The old 'never mix niacinamide and vitamin C' warning is a myth, and serums with both have done well in trials.10
- HydroquinoneFine together. Dark spot routines often stack brightening ingredients like these.11,12,13
- Azelaic acidFine together. These are common partners in dark spot routines.11,14,15
- Tranexamic acidFine together. Both are dark spot ingredients and they're often layered.15,16
- Arbutin, Kojic acid, GlutathioneFine together. Brightening ingredients like these are often stacked in dark spot routines.17,18,19
- PeptidesFine together. Peptides are gentle and sit happily alongside other anti-ageing ingredients.20,21,22
In 1,533 products in my routine checker.
More: best ingredients for dark spots
Check your routine with vitamin CNiacinamide
Also called vitamin B3
Niacinamide is vitamin B3. It helps your skin make more of its own ceramides, it calms redness, it can take the edge off oiliness and it slows down the pigment that turns into dark marks. On top of that, it's one of the gentlest actives going, which is why it's in so many K-beauty serums.
Morning, night or both. The studies that showed results used 2% to 5%, so you don't need a 20% serum (and very high amounts make some people flush). One niacinamide product in a routine is plenty.
Oily skin, dark marks, redness, a tired barrier. Most skin types get on with it.
What not to mix with niacinamide
Work well together
- Tranexamic acidThese help each other. Tranexamic acid and niacinamide have been tested together for dark spots.23,24,25
- Azelaic acidThese help each other. Both calm redness and fade marks, and neither cancels the other out.16,26
- ZincThese help each other. Zinc and niacinamide are a common pairing for oily, spot-prone skin.27,28,29
- PanthenolThese help each other. Niacinamide and panthenol have been used together to repair the skin barrier.30
Fine together
- Tretinoin, Adapalene, Tazarotene, RetinolFine together. Niacinamide is calming and lots of retinol products already have it in, and a niacinamide moisturiser has been tested alongside acne retinoids.31,32
- Vitamin CFine together. The old 'never mix niacinamide and vitamin C' warning is a myth, and serums with both have done well in trials.10
- HydroquinoneFine together. Dark spot routines often stack brightening ingredients like these.11,12,13
- Benzoyl peroxide, BHAFine together. Niacinamide is often used alongside acne treatments like these.29,26,33
- Arbutin, Kojic acid, GlutathioneFine together. Brightening ingredients like these are often stacked in dark spot routines.17,18,19
- PeptidesFine together. Peptides are gentle and sit happily alongside other anti-ageing ingredients.20,21,22
In 1,194 products in my routine checker.
My review: Anua Niacinamide 10% + TXA 4% Serum · More: best ingredients for dark spots
Check your routine with niacinamideTranexamic acid
Also called TXA
Tranexamic acid started out as a medicine to stop bleeding, and now it's one of the most-used ingredients for dark spots and melasma. It calms the signals that tell your skin to make extra pigment. Because it's gentle, it rarely stings.
Morning or night. Most things sit happily alongside it, and it's often paired with niacinamide.
Dark spots and melasma, especially if your skin is sensitive.
What not to mix with tranexamic acid
Work well together
- NiacinamideThese help each other. Tranexamic acid and niacinamide have been tested together for dark spots.23,24,25
Fine together
- HydroquinoneFine together. Dark spot routines often stack brightening ingredients like these.11,12,13
- Azelaic acidFine together. These are common partners in dark spot routines.11,14,15
- Vitamin CFine together. Both are dark spot ingredients and they're often layered.15,16
- AHAsFine together. Tranexamic acid has even been paired with mandelic acid to help it get into the skin.34
- Arbutin, Kojic acid, GlutathioneFine together. Brightening ingredients like these are often stacked in dark spot routines.17,18,19
In 166 products in my routine checker.
My review: Anua Niacinamide 10% + TXA 4% Serum · More: best ingredients for dark spots
Check your routine with tranexamic acidAzelaic acid
Azelaic acid is a gentle acid that calms redness, helps with spots and fades the marks they leave by slowing down pigment. It's one of the few actives that's often suggested for rosacea. Skincare versions are usually around 10%, and the stronger 15% to 20% creams are prescription in the UK.
Once or twice a day. Some tingling in the first week or two is normal, so start every other day if you're sensitive.
Rosacea, redness, spots and dark marks. If you're pregnant, it's often mentioned as an option, but check with your doctor first.
What not to mix with azelaic acid
Work well together
- NiacinamideThese help each other. Both calm redness and fade marks, and neither cancels the other out.16,26
- Panthenol, CentellaThese help each other. Panthenol and centella calm skin, which makes strong actives easier to live with.35,36,37
- Ceramides, Hyaluronic acid, UreaThese help each other. A hydrating, barrier-friendly product helps your skin cope with strong actives.38,39,40
Fine together
- HydroquinoneFine together. Dark spot routines often stack brightening ingredients like these.11,12,13
- Tranexamic acid, Vitamin CFine together. These are common partners in dark spot routines.11,14,15
- Tretinoin, Adapalene, Tazarotene, RetinolFine together. Azelaic acid and retinoids are a common acne pairing. Start slowly if your skin is sensitive.41,42,43
- Arbutin, Kojic acid, GlutathioneFine together. Brightening ingredients like these are often stacked in dark spot routines.17,18,19
- SulphurFine together. Sulphur and azelaic acid are both used for spots and rosacea.44,45,46
In 174 products in my routine checker.
My review: Anua Azelaic Acid 15 Intense Calming Serum · More: best ingredients for dark spots
Check your routine with azelaic acidAlpha arbutin
Also called arbutin
Alpha arbutin is a brightening ingredient that slows down the enzyme your skin uses to make pigment. You'll find it in in a lot of Korean and Japanese dark spot serums, and it's gentle.
Morning or night. It's often stacked with niacinamide, vitamin C or tranexamic acid.
Dark spots and uneven tone, including sensitive skin.
What not to mix with alpha arbutin
Fine together
- Kojic acid, Glutathione, Hydroquinone, Tranexamic acid, Azelaic acid, Niacinamide, Vitamin CFine together. Brightening ingredients like these are often stacked in dark spot routines.17,18,19
More: best ingredients for dark spots
Check your routine with alpha arbutinAHAs
Also called glycolic, lactic and mandelic acid
AHAs are water-loving acids that loosen the glue holding dead skin cells on the surface. Glycolic acid is the smallest and strongest, lactic acid is a bit gentler and adds hydration, and mandelic acid is the gentlest of the three. Used regularly, they smooth rough texture and brighten dullness.
Usually at night, a few times a week to start. They make your skin more sensitive to the sun, so sunscreen the next day isn't optional.
Rough texture and dullness. Mandelic or lactic acid if you're sensitive.
What not to mix with AHAs
Space them out
- Tretinoin, Adapalene, Tazarotene, RetinolBoth are strong. Together on the same night they're likely to irritate, so use them on different nights (or one morning, one night). A plain moisturiser on top can help with the sting. (Products made with both in one formula are different, those are balanced to be gentler.)47,48,49
- Vitamin CBoth like a low pH, so layering them at the same time is a recipe for stinging. Try them at different times of day.4,5
- PHAsThat's two exfoliating acids at once. PHAs are gentle, but you probably only need one of these at a time.50,5
- Tea tree oilTea tree oil can irritate on its own, so adding it to a strong active may be too much. Use them at different times or go slowly.51,52,53
Work well together
Fine together
- Tranexamic acidFine together. Tranexamic acid has even been paired with mandelic acid to help it get into the skin.34
In 799 products in my routine checker.
Check your routine with AHAsBHA
Also called salicylic acid
Salicylic acid is oil-soluble, so it gets inside the pore instead of just working on the surface. It helps clear blackheads and congestion and calms spots a little, which is why it's the acid most people with oily skin reach for.
Start a few times a week, at night. Watch for dryness if you're using other spot treatments too.
Oily skin, blackheads, clogged pores and spots.
What not to mix with BHA (salicylic acid)
Space them out
- Tretinoin, Adapalene, Tazarotene, RetinolBoth are strong. Together on the same night they're likely to irritate, so use them on different nights (or one morning, one night). A plain moisturiser on top can help with the sting. (Products made with both in one formula are different, those are balanced to be gentler.)47,48,49
- Vitamin CBoth like a low pH, so layering them at the same time is a recipe for stinging. Try them at different times of day.4,5
- PHAsThat's two exfoliating acids at once. PHAs are gentle, but you probably only need one of these at a time.50,5
- Tea tree oilTea tree oil can irritate on its own, so adding it to a strong active may be too much. Use them at different times or go slowly.51,52,53
Work well together
Fine together
- NiacinamideFine together. Niacinamide is often used alongside acne treatments like these.29,26,33
- Benzoyl peroxideFine together for most people. Salicylic acid and benzoyl peroxide have been used side by side for spots, just watch for dryness.54,55,56
In 759 products in my routine checker.
Check your routine with BHA (salicylic acid)PHAs
Also called gluconolactone and lactobionic acid
PHAs exfoliate like AHAs, but their bigger molecules sink in more slowly, so they sting a lot less. They also pull in water. They're the acid people usually suggest if glycolic acid is too much for your skin.
Morning or night. Because they're gentle, some people use them daily, but you still only need one acid at a time.
Sensitive skin that wants a bit of exfoliation.
What not to mix with PHAs
Space them out
Fine together
Retinol
Also called vitamin A
Retinol is a form of vitamin A that you can buy without a prescription. Your skin has to convert it into retinoic acid before it works, which makes it slower and gentler than tretinoin. Over months it softens fine lines, fades marks and keeps pores clearer. Retinal (retinaldehyde) is one step closer to retinoic acid, so it works a bit faster.
At night only, starting two or three nights a week and building up. Expect some dryness or flaking at first. Use sunscreen every day, and skip it if you're pregnant or trying to be.
Fine lines, texture, dark marks and clogged pores.
What not to mix with retinol
Space them out
- Benzoyl peroxideBenzoyl peroxide can break retinoids down. To be safe, use them at different times of day.59
- AHAs, BHABoth are strong. Together on the same night they're likely to irritate, so use them on different nights (or one morning, one night). A plain moisturiser on top can help with the sting. (Products made with both in one formula are different, those are balanced to be gentler.)47,48,49
- Vitamin CYou can use both, but it's easiest to split them: vitamin C in the morning, the retinoid at night.1,2,3
- Tea tree oilTea tree oil can irritate on its own, so adding it to a strong active may be too much. Use them at different times or go slowly.51,52,53
- SulphurBoth can be drying. Use them at different times of day or on different days.26,42
Work well together
- HydroquinoneThese help each other. Hydroquinone and a retinoid are put together on purpose in prescription dark spot creams.60,61,62
- SunscreenA great pair. Retinoid at night and sunscreen every morning is the classic anti-ageing routine.63,64,65
- Panthenol, CentellaThese help each other. Panthenol and centella calm skin, which makes strong actives easier to live with.35,36,37
- Ceramides, Hyaluronic acid, UreaThese help each other. A hydrating, barrier-friendly product helps your skin cope with strong actives.38,39,40
Fine together
- NiacinamideFine together. Niacinamide is calming and lots of retinol products already have it in, and a niacinamide moisturiser has been tested alongside acne retinoids.31,32
- Azelaic acidFine together. Azelaic acid and retinoids are a common acne pairing. Start slowly if your skin is sensitive.41,42,43
- BakuchiolFine together, but bakuchiol does a similar job to a retinoid, so you may not need both.66,67,68
- PHAsFine together for most people. PHAs are the gentlest acids and sting much less than AHAs, but start slowly with a retinoid.50,57,58
- PeptidesFine together. Peptides are gentle and sit happily alongside other anti-ageing ingredients.20,21,22
In 1,248 products in my routine checker.
Check your routine with retinolTretinoin
Also called prescription retinoic acid
Tretinoin is retinoic acid itself, the form of vitamin A your skin actually uses, so there's no converting to do. You need a prescription for it in the UK and the US, and it's the most studied cream there is for both acne and sun damage. Tazarotene is a stronger prescription retinoid in the same family.
At night, a pea-sized amount, usually starting a few nights a week. Your prescriber will tell you how to build up. Not for pregnancy.
Acne and sun damage (fine lines included), under a prescriber's eye.
What not to mix with tretinoin
Don’t layer
- Benzoyl peroxideBenzoyl peroxide breaks tretinoin down, so putting them on together can stop the tretinoin working. Use one in the morning and one at night.59
Space them out
- AHAs, BHABoth are strong. Together on the same night they're likely to irritate, so use them on different nights (or one morning, one night). A plain moisturiser on top can help with the sting. (Products made with both in one formula are different, those are balanced to be gentler.)47,48,49
- Vitamin CYou can use both, but it's easiest to split them: vitamin C in the morning, the retinoid at night.1,2,3
- Tea tree oilTea tree oil can irritate on its own, so adding it to a strong active may be too much. Use them at different times or go slowly.51,52,53
- SulphurBoth can be drying. Use them at different times of day or on different days.26,42
Work well together
- HydroquinoneThese help each other. Hydroquinone and a retinoid are put together on purpose in prescription dark spot creams.60,61,62
- SunscreenA great pair. Retinoid at night and sunscreen every morning is the classic anti-ageing routine.63,64,65
- Panthenol, CentellaThese help each other. Panthenol and centella calm skin, which makes strong actives easier to live with.35,36,37
- Ceramides, Hyaluronic acid, UreaThese help each other. A hydrating, barrier-friendly product helps your skin cope with strong actives.38,39,40
Fine together
- NiacinamideFine together. Niacinamide is calming and lots of retinol products already have it in, and a niacinamide moisturiser has been tested alongside acne retinoids.31,32
- Azelaic acidFine together. Azelaic acid and retinoids are a common acne pairing. Start slowly if your skin is sensitive.41,42,43
- BakuchiolFine together, but bakuchiol does a similar job to a retinoid, so you may not need both.66,67,68
- PHAsFine together for most people. PHAs are the gentlest acids and sting much less than AHAs, but start slowly with a retinoid.50,57,58
- PeptidesFine together. Peptides are gentle and sit happily alongside other anti-ageing ingredients.20,21,22
In 27 products in my routine checker.
My review: Dermatica (tretinoin), tretinoin vs tazarotene
Check your routine with tretinoinAdapalene
Adapalene is a retinoid made for acne. It unclogs pores and calms inflammation with less irritation than tretinoin. In the US you can buy 0.1% over the counter, but in the UK it's prescription-only.
At night, usually starting every other night. It's often paired with benzoyl peroxide, and there are gels with both in one tube.
Spots and clogged pores.
What not to mix with adapalene
Space them out
- AHAs, BHABoth are strong. Together on the same night they're likely to irritate, so use them on different nights (or one morning, one night). A plain moisturiser on top can help with the sting. (Products made with both in one formula are different, those are balanced to be gentler.)47,48,49
- Vitamin CYou can use both, but it's easiest to split them: vitamin C in the morning, the retinoid at night.1,2,3
- Tea tree oilTea tree oil can irritate on its own, so adding it to a strong active may be too much. Use them at different times or go slowly.51,52,53
- SulphurBoth can be drying. Use them at different times of day or on different days.26,42
Work well together
- HydroquinoneThese help each other. Hydroquinone and a retinoid are put together on purpose in prescription dark spot creams.60,61,62
- SunscreenA great pair. Retinoid at night and sunscreen every morning is the classic anti-ageing routine.63,64,65
- Panthenol, CentellaThese help each other. Panthenol and centella calm skin, which makes strong actives easier to live with.35,36,37
- Ceramides, Hyaluronic acid, UreaThese help each other. A hydrating, barrier-friendly product helps your skin cope with strong actives.38,39,40
Fine together
- NiacinamideFine together. Niacinamide is calming and lots of retinol products already have it in, and a niacinamide moisturiser has been tested alongside acne retinoids.31,32
- Benzoyl peroxideFine together. Adapalene and benzoyl peroxide are made to work as a pair, there are even gels with both in one tube.69,70,71
- Azelaic acidFine together. Azelaic acid and retinoids are a common acne pairing. Start slowly if your skin is sensitive.41,42,43
- BakuchiolFine together, but bakuchiol does a similar job to a retinoid, so you may not need both.66,67,68
- PHAsFine together for most people. PHAs are the gentlest acids and sting much less than AHAs, but start slowly with a retinoid.50,57,58
- PeptidesFine together. Peptides are gentle and sit happily alongside other anti-ageing ingredients.20,21,22
In 11 products in my routine checker.
Check your routine with adapaleneBakuchiol
Bakuchiol is a plant extract often sold as a gentle retinol alternative. It doesn't work the same way as a retinoid, but small studies found it helped with fine lines and was less irritating than retinol.
Morning or night. Since it does a similar job to a retinoid, you may not need both if you already use one.
Anyone who finds retinol too much.
What not to mix with bakuchiol
Fine together
Peptides
Peptides are short chains of amino acids that act like messengers in the skin. Some, like Matrixyl, have been studied for firmness and fine lines, and copper peptides for repair. The results are subtler than a retinoid, but they're very gentle.
Either end of the day. They sit happily with most other anti-ageing ingredients.
Mature skin and anyone who wants anti-ageing without the sting.
What not to mix with peptides
Fine together
My review: Medicube Collagen Night Wrapping Mask
Check your routine with peptidesBenzoyl peroxide
Also called BPO
Benzoyl peroxide kills the bacteria behind spots by releasing oxygen into the pore, and bacteria don't become resistant to it. Expect some dryness, and it bleaches towels and pillowcases (white ones are your friend here).
Once a day to start, often as a short-contact wash. Keep it away from tretinoin, it breaks it down.
Spots, especially red, inflamed ones.
What not to mix with benzoyl peroxide
Don’t layer
Space them out
- Retinol, TazaroteneBenzoyl peroxide can break retinoids down. To be safe, use them at different times of day.59
- Tea tree oilTea tree oil can irritate on its own, so adding it to a strong active may be too much. Use them at different times or go slowly.51,52,53
- SulphurBoth can be drying. Use them at different times of day or on different days.26,42
Work well together
Fine together
- AdapaleneFine together. Adapalene and benzoyl peroxide are made to work as a pair, there are even gels with both in one tube.69,70,71
- NiacinamideFine together. Niacinamide is often used alongside acne treatments like these.29,26,33
- BHAFine together for most people. Salicylic acid and benzoyl peroxide have been used side by side for spots, just watch for dryness.54,55,56
In 51 products in my routine checker.
Check your routine with benzoyl peroxideZinc
Also called zinc PCA
Zinc PCA turns up in oil-control and spot products. It's linked to less shine and calmer spots, and it pairs nicely with niacinamide.
Whenever it suits your routine.
Oily, spot-prone skin.
What not to mix with zinc
Work well together
- NiacinamideThese help each other. Zinc and niacinamide are a common pairing for oily, spot-prone skin.27,28,29
Sulphur
Also called sulfur
Sulphur has been used on spots and rosacea for a very long time. Sulphur dries out spots and has an antifungal side too. Yes, some sulphur products smell a bit eggy.
Often as a mask or spot treatment. It can be drying, so don't pile it on with other drying actives.
Spots and rosacea.
What not to mix with sulphur
Space them out
Fine together
- Azelaic acidFine together. Sulphur and azelaic acid are both used for spots and rosacea.44,45,46
Tea tree oil
Tea tree oil has some evidence for mild spots. As an essential oil, though, it can irritate on its own, and it's a common allergy trigger.
Low amounts only, and go slowly if you use other strong actives.
Mild spots, if your skin tolerates it.
What not to mix with tea tree oil
Space them out
Hyaluronic acid
Also called sodium hyaluronate
Hyaluronic acid holds onto water and plumps up the top layers of your skin. The smaller forms sink in further, the bigger ones sit on the surface and smooth it. Hyaluronic acid hydrates but doesn't seal moisture in, so put a moisturiser on top.
Morning or night, on damp skin, then moisturiser.
Every skin type, and it helps strong actives feel less harsh.
What not to mix with hyaluronic acid
Work well together
- Tretinoin, Adapalene, Tazarotene, Retinol, AHAs, BHA, Benzoyl peroxide, Azelaic acidThese help each other. A hydrating, barrier-friendly product helps your skin cope with strong actives.38,39,40
My review: Torriden Dive-In Serum
Check your routine with hyaluronic acidCeramides
Ceramides are fats that make up a big part of your skin's barrier, the mortar between the bricks. Topping them up cuts down water loss and helps irritated or over-exfoliated skin settle.
Usually in a moisturiser, whenever you like.
Dry, sensitive or irritated skin, and anyone using retinoids or acids.
What not to mix with ceramides
Work well together
- Tretinoin, Adapalene, Tazarotene, Retinol, AHAs, BHA, Benzoyl peroxide, Azelaic acidThese help each other. A hydrating, barrier-friendly product helps your skin cope with strong actives.38,39,40
My review: Aestura Atobarrier 365 Cream
Check your routine with ceramidesPanthenol
Also called vitamin B5
Panthenol is pro-vitamin B5. Your skin turns it into pantothenic acid, which pulls in moisture and supports the barrier. It's a big part of why so many soothing creams feel soothing.
Any time of day.
Dry or irritated skin.
What not to mix with panthenol
Work well together
- Tretinoin, Adapalene, Tazarotene, Retinol, AHAs, BHA, Benzoyl peroxide, Azelaic acidThese help each other. Panthenol and centella calm skin, which makes strong actives easier to live with.35,36,37
- NiacinamideThese help each other. Niacinamide and panthenol have been used together to repair the skin barrier.30
Centella asiatica
Also called cica, madecassoside
Centella, or cica, is a plant whose compounds (madecassoside and asiaticoside) calm irritation and support skin repair. You'll see it all over Korean calming skincare.
Morning or night. Strong actives are easier to live with when it's in your routine.
Calming redness and irritation.
What not to mix with centella
Work well together
- Tretinoin, Adapalene, Tazarotene, Retinol, AHAs, BHA, Benzoyl peroxide, Azelaic acidThese help each other. Panthenol and centella calm skin, which makes strong actives easier to live with.35,36,37
My review: SKIN1004 Madagascar Centella range
Check your routine with centellaSnail mucin
Also called snail secretion filtrate
Snail secretion filtrate is a mix of glycoproteins, a little hyaluronic acid and small amounts of glycolic acid. It hydrates and helps skin recover, and it layers without feeling sticky.
After toner, morning or night.
Dehydrated skin and marks that are slow to fade.
What not to mix with snail mucin
No clashes in my checker for this one, it plays nicely with pretty much everything.
Check your routine with snail mucinSunscreen
Also called SPF
UV filters absorb or reflect UV light before it damages your skin. Daily SPF prevents burning, dark spots and most visible ageing, and it's what makes acids and retinoids safe to use. Korean sunscreens are loved for their light textures.
Every morning, as the last step – and top up if you're outside for long.
Everyone. This is the one step I'd never skip.
What not to mix with sunscreen
Work well together
In 4,551 products in my routine checker.
My review: Korean sunscreens I've tried
Check your routine with sunscreenCan you use these together?
Here’s every pairing my routine checker knows about, in one place. If you’ve got your products to hand, it’s quicker to pop them into the routine checker and let it do the matching.
Don’t layer
Space them out
- Retinol + Benzoyl peroxide · Tazarotene + Benzoyl peroxideBenzoyl peroxide can break retinoids down. To be safe, use them at different times of day.59
- Tretinoin + AHAs · Tretinoin + BHA · Adapalene + AHAs · Adapalene + BHA · Tazarotene + AHAs · Tazarotene + BHA · Retinol + AHAs · Retinol + BHABoth are strong. Together on the same night they're likely to irritate, so use them on different nights (or one morning, one night). A plain moisturiser on top can help with the sting. (Products made with both in one formula are different, those are balanced to be gentler.)47,48,49
- Tretinoin + Vitamin C · Adapalene + Vitamin C · Tazarotene + Vitamin C · Retinol + Vitamin CYou can use both, but it's easiest to split them: vitamin C in the morning, the retinoid at night.1,2,3
- AHAs + Vitamin C · BHA + Vitamin CBoth like a low pH, so layering them at the same time is a recipe for stinging. Try them at different times of day.4,5
- PHAs + AHAs · PHAs + BHAThat's two exfoliating acids at once. PHAs are gentle, but you probably only need one of these at a time.50,5
- Tea tree oil + Tretinoin · Tea tree oil + Adapalene · Tea tree oil + Tazarotene · Tea tree oil + Retinol · Tea tree oil + Benzoyl peroxide · Tea tree oil + AHAs · Tea tree oil + BHATea tree oil can irritate on its own, so adding it to a strong active may be too much. Use them at different times or go slowly.51,52,53
- Sulphur + Tretinoin · Sulphur + Adapalene · Sulphur + Tazarotene · Sulphur + Retinol · Sulphur + Benzoyl peroxideBoth can be drying. Use them at different times of day or on different days.26,42
Work well together
- Tranexamic acid + NiacinamideThese help each other. Tranexamic acid and niacinamide have been tested together for dark spots.23,24,25
- Vitamin C + SunscreenA great morning pair. Vitamin C under your sunscreen gives you extra protection on top of the SPF.6,7,8
- Hydroquinone + Tretinoin · Hydroquinone + Adapalene · Hydroquinone + Tazarotene · Hydroquinone + RetinolThese help each other. Hydroquinone and a retinoid are put together on purpose in prescription dark spot creams.60,61,62
- Azelaic acid + NiacinamideThese help each other. Both calm redness and fade marks, and neither cancels the other out.16,26
- Vitamin C + Vitamin EThese help each other. Vitamin E and ferulic acid keep vitamin C stable and boost its protection.9,6
- Tretinoin + Sunscreen · Adapalene + Sunscreen · Tazarotene + Sunscreen · Retinol + SunscreenA great pair. Retinoid at night and sunscreen every morning is the classic anti-ageing routine.63,64,65
- Zinc + NiacinamideThese help each other. Zinc and niacinamide are a common pairing for oily, spot-prone skin.27,28,29
- Panthenol + Tretinoin · Panthenol + Adapalene · Panthenol + Tazarotene · Panthenol + Retinol · Panthenol + AHAs · Panthenol + BHA · Panthenol + Benzoyl peroxide · Panthenol + Azelaic acid · Centella + Tretinoin · Centella + Adapalene · Centella + Tazarotene · Centella + Retinol · Centella + AHAs · Centella + BHA · Centella + Benzoyl peroxide · Centella + Azelaic acidThese help each other. Panthenol and centella calm skin, which makes strong actives easier to live with.35,36,37
- Ceramides + Tretinoin · Ceramides + Adapalene · Ceramides + Tazarotene · Ceramides + Retinol · Ceramides + AHAs · Ceramides + BHA · Ceramides + Benzoyl peroxide · Ceramides + Azelaic acid · Hyaluronic acid + Tretinoin · Hyaluronic acid + Adapalene · Hyaluronic acid + Tazarotene · Hyaluronic acid + Retinol · Hyaluronic acid + AHAs · Hyaluronic acid + BHA · Hyaluronic acid + Benzoyl peroxide · Hyaluronic acid + Azelaic acid · Urea + Tretinoin · Urea + Adapalene · Urea + Tazarotene · Urea + Retinol · Urea + AHAs · Urea + BHA · Urea + Benzoyl peroxide · Urea + Azelaic acidThese help each other. A hydrating, barrier-friendly product helps your skin cope with strong actives.38,39,40
- Panthenol + NiacinamideThese help each other. Niacinamide and panthenol have been used together to repair the skin barrier.30
Fine together
- Tretinoin + Niacinamide · Adapalene + Niacinamide · Tazarotene + Niacinamide · Retinol + NiacinamideFine together. Niacinamide is calming and lots of retinol products already have it in, and a niacinamide moisturiser has been tested alongside acne retinoids.31,32
- Niacinamide + Vitamin CFine together. The old 'never mix niacinamide and vitamin C' warning is a myth, and serums with both have done well in trials.10
- Adapalene + Benzoyl peroxideFine together. Adapalene and benzoyl peroxide are made to work as a pair, there are even gels with both in one tube.69,70,71
- Hydroquinone + Vitamin C · Hydroquinone + Azelaic acid · Hydroquinone + Tranexamic acid · Hydroquinone + NiacinamideFine together. Dark spot routines often stack brightening ingredients like these.11,12,13
- Azelaic acid + Tranexamic acid · Azelaic acid + Vitamin CFine together. These are common partners in dark spot routines.11,14,15
- Tranexamic acid + Vitamin CFine together. Both are dark spot ingredients and they're often layered.15,16
- Azelaic acid + Tretinoin · Azelaic acid + Adapalene · Azelaic acid + Tazarotene · Azelaic acid + RetinolFine together. Azelaic acid and retinoids are a common acne pairing. Start slowly if your skin is sensitive.41,42,43
- Bakuchiol + Tretinoin · Bakuchiol + Adapalene · Bakuchiol + Tazarotene · Bakuchiol + RetinolFine together, but bakuchiol does a similar job to a retinoid, so you may not need both.66,67,68
- Benzoyl peroxide + Niacinamide · BHA + NiacinamideFine together. Niacinamide is often used alongside acne treatments like these.29,26,33
- BHA + Benzoyl peroxideFine together for most people. Salicylic acid and benzoyl peroxide have been used side by side for spots, just watch for dryness.54,55,56
- Tranexamic acid + AHAsFine together. Tranexamic acid has even been paired with mandelic acid to help it get into the skin.34
- Arbutin + Kojic acid · Arbutin + Glutathione · Arbutin + Hydroquinone · Arbutin + Tranexamic acid · Arbutin + Azelaic acid · Arbutin + Niacinamide · Arbutin + Vitamin C · Kojic acid + Glutathione · Kojic acid + Hydroquinone · Kojic acid + Tranexamic acid · Kojic acid + Azelaic acid · Kojic acid + Niacinamide · Kojic acid + Vitamin C · Glutathione + Hydroquinone · Glutathione + Tranexamic acid · Glutathione + Azelaic acid · Glutathione + Niacinamide · Glutathione + Vitamin CFine together. Brightening ingredients like these are often stacked in dark spot routines.17,18,19
- PHAs + Tretinoin · PHAs + Adapalene · PHAs + Tazarotene · PHAs + RetinolFine together for most people. PHAs are the gentlest acids and sting much less than AHAs, but start slowly with a retinoid.50,57,58
- Sulphur + Azelaic acidFine together. Sulphur and azelaic acid are both used for spots and rosacea.44,45,46
- Peptides + Tretinoin · Peptides + Adapalene · Peptides + Tazarotene · Peptides + Retinol · Peptides + Vitamin C · Peptides + NiacinamideFine together. Peptides are gentle and sit happily alongside other anti-ageing ingredients.20,21,22
Questions people ask
What skincare ingredients should you not mix?
The big ones are a retinoid with an AHA or BHA on the same night, benzoyl peroxide with tretinoin, and two exfoliating acids at once. Vitamin C with acids, or with a retinoid, is easier split between morning and night. Most other combinations are fine.
Can you use niacinamide and vitamin C together?
Yes. The old warning that they cancel each other out is a myth, and serums with both have done well in trials.
Can you use retinol and niacinamide together?
Yes. Niacinamide is calming and lots of retinol products already have it in.
Can you use retinol and vitamin C together?
You can use both, but it's easiest to split them: vitamin C in the morning and the retinol at night.
What not to mix with salicylic acid?
Don't layer it with a retinoid on the same night, and go easy with other acids and vitamin C at the same time. It's fine with niacinamide, and fine with benzoyl peroxide for most people if you watch for dryness.
Got a specific product in mind? My skincare ingredient checker flags pore cloggers and fungal acne triggers (plus rosacea, eczema and more) if you paste in the ingredients, and my dark spot guide goes deeper on brightening ingredients.
Sources (72)
- Siddiqui and colleagues, tretinoin compared with other anti-ageing products, 2024. pubmed.ncbi.nlm.nih.gov/39348007/
- Lin and colleagues, comparing anti-ageing ingredients, 2025. pubmed.ncbi.nlm.nih.gov/40707570/
- Correia and Magina, vitamin C systematic review, 2023. pubmed.ncbi.nlm.nih.gov/37128827/
- Pinnell and colleagues, how much vitamin C skin can take up, 2001. pubmed.ncbi.nlm.nih.gov/11207686/
- Sharad, glycolic acid review, 2013. pubmed.ncbi.nlm.nih.gov/24399880/
- Murray and colleagues, vitamin C, E and ferulic serum adds sun protection, 2008. pubmed.ncbi.nlm.nih.gov/18603326/
- Alvarez and colleagues, ingredients dermatologists recommend, 2025. pubmed.ncbi.nlm.nih.gov/40233838/
- Bissett, common cosmeceuticals, 2009. pubmed.ncbi.nlm.nih.gov/19695474/
- Lin and colleagues, ferulic acid steadies vitamin C and E, 2005. pubmed.ncbi.nlm.nih.gov/16185284/
- Rocio and colleagues, niacinamide, vitamin C and tranexamic acid serum trial, 2025. pubmed.ncbi.nlm.nih.gov/40062688/
- Philipp-Dormston, step-by-step dark spot combinations, 2024. pubmed.ncbi.nlm.nih.gov/38800358/
- Hu and colleagues, newer pigment treatments, 2022. pubmed.ncbi.nlm.nih.gov/34114938/
- Davis and Callender, marks after spots in darker skin, 2010. pubmed.ncbi.nlm.nih.gov/20725554/
- Tan and colleagues, post-acne marks treatments review, 2022. pubmed.ncbi.nlm.nih.gov/34525885/
- Austin and colleagues, dark spot trials review, 2019. pubmed.ncbi.nlm.nih.gov/31741361/
- Gonzalez-Molina and colleagues, dark spot treatments review, 2022. pubmed.ncbi.nlm.nih.gov/35642229/
- Tantanasrigul and colleagues, arbutin and kojic acid trial, 2025. pubmed.ncbi.nlm.nih.gov/39555866/
- Gabhane and colleagues, arbutin with sunscreen study, 2025. pubmed.ncbi.nlm.nih.gov/39943675/
- Sarkar and colleagues, dark spot treatments review, 2023. pubmed.ncbi.nlm.nih.gov/38099013/
- Imhof and Leuthard, over-the-counter anti-ageing review, 2021. pubmed.ncbi.nlm.nih.gov/32882685/
- Chan and colleagues, cosmeceuticals for ageing skin, 2024. pubmed.ncbi.nlm.nih.gov/39233460/
- Draelos and colleagues, top anti-ageing actives, 2024. pubmed.ncbi.nlm.nih.gov/38881445/
- Ghasemiyeh and colleagues, tranexamic acid with niacinamide trial, 2025. pubmed.ncbi.nlm.nih.gov/41315336/
- Suliman and colleagues, newer dark spot treatments, 2025. pubmed.ncbi.nlm.nih.gov/41307217/
- Calacattawi and colleagues, tranexamic acid meta-analysis, 2024. pubmed.ncbi.nlm.nih.gov/38843906/
- Liu and colleagues, Cochrane review of azelaic acid, salicylic acid and niacinamide, 2020. pubmed.ncbi.nlm.nih.gov/32356369/
- Yee and colleagues, zinc for acne meta-analysis, 2020. pubmed.ncbi.nlm.nih.gov/32860489/
- Brandt, zinc for acne review, 2013. pubmed.ncbi.nlm.nih.gov/23652948/
- Walocko and colleagues, niacinamide for acne, 2017. pubmed.ncbi.nlm.nih.gov/28220628/
- Liu and colleagues, niacinamide and panthenol routine trial, 2026. pubmed.ncbi.nlm.nih.gov/42686896/
- Handler and colleagues, retinol and niacinamide in one product, 2022. pubmed.ncbi.nlm.nih.gov/35816074/
- Tempark and colleagues, niacinamide moisturiser alongside acne retinoids, 2024. pubmed.ncbi.nlm.nih.gov/38299457/
- Yang and colleagues, Cochrane review of benzoyl peroxide, 2020. pubmed.ncbi.nlm.nih.gov/32175593/
- Jeon and colleagues, tranexamic acid with mandelic acid, 2025. pubmed.ncbi.nlm.nih.gov/40936315/
- Ebner and colleagues, panthenol in skin conditions, 2002. pubmed.ncbi.nlm.nih.gov/12113650/
- Proksch and colleagues, 70 years of panthenol, 2017. pubmed.ncbi.nlm.nih.gov/28503966/
- Su and colleagues, centella, ceramide and panthenol cream study, 2025. pubmed.ncbi.nlm.nih.gov/40682399/
- van Zuuren and colleagues, Cochrane review of moisturisers, 2017. pubmed.ncbi.nlm.nih.gov/28432721/
- Wollenberg and colleagues, basic emollients review, 2025. pubmed.ncbi.nlm.nih.gov/40265493/
- Kim and colleagues, sensitive skin review, 2025. pubmed.ncbi.nlm.nih.gov/40736518/
- Purdy and de Berker, acne treatments review, 2011. pubmed.ncbi.nlm.nih.gov/21477388/
- Reynolds and colleagues, acne treatment guidelines, 2024. pubmed.ncbi.nlm.nih.gov/38300170/
- Petrovici and colleagues, azelaic acid review, 2025. pubmed.ncbi.nlm.nih.gov/41011144/
- van Zuuren and colleagues, Cochrane rosacea review, 2011. pubmed.ncbi.nlm.nih.gov/21692773/
- Sharma and colleagues, rosacea management review, 2022. pubmed.ncbi.nlm.nih.gov/35104917/
- Hua and colleagues, rosacea redness treatments review, 2025. pubmed.ncbi.nlm.nih.gov/39478371/
- Rendon and colleagues, tretinoin cream and glycolic peels on a schedule, 2008. pubmed.ncbi.nlm.nih.gov/19090343/
- Fang and colleagues, skin lipids calm retinol irritation, 2024. pubmed.ncbi.nlm.nih.gov/38628085/
- Loden, moisturisers and the skin barrier, 2003. pubmed.ncbi.nlm.nih.gov/14572299/
- Edison and colleagues, PHA compared with AHA, 2004. pubmed.ncbi.nlm.nih.gov/15002657/
- Ye and colleagues, tea tree oil for acne meta-analysis, 2026. pubmed.ncbi.nlm.nih.gov/42098589/
- Kairey and colleagues, tea tree oil trials review, 2023. pubmed.ncbi.nlm.nih.gov/37033604/
- Cao and colleagues, Cochrane review of complementary acne treatments, 2015. pubmed.ncbi.nlm.nih.gov/25597924/
- Akarsu and colleagues, salicylic acid added to benzoyl peroxide, 2012. pubmed.ncbi.nlm.nih.gov/22035285/
- Bowe and Shalita, over-the-counter acne treatments, 2008. pubmed.ncbi.nlm.nih.gov/18786494/
- Arif, salicylic acid review, 2015. pubmed.ncbi.nlm.nih.gov/26347269/
- Grimes and colleagues, PHAs for sun-damaged skin, 2004. pubmed.ncbi.nlm.nih.gov/15002656/
- Jarzabek-Perz and colleagues, gluconolactone and skin moisture, 2021. pubmed.ncbi.nlm.nih.gov/33769633/
- Torok and Pillai, benzoyl peroxide breaks down tretinoin, 2011. pubmed.ncbi.nlm.nih.gov/21637905/
- Arellano and colleagues, hydroquinone and tretinoin cream, 2012. pubmed.ncbi.nlm.nih.gov/21623930/
- Wang and colleagues, triple cream for dark spots trial, 2020. pubmed.ncbi.nlm.nih.gov/31494973/
- McKesey and colleagues, dark spot evidence review, 2020. pubmed.ncbi.nlm.nih.gov/31802394/
- Hughes and colleagues, daily sunscreen and skin ageing trial, 2013. pubmed.ncbi.nlm.nih.gov/23732711/
- Seite and Fourtanier, the benefit of daily sun protection, 2008. pubmed.ncbi.nlm.nih.gov/18410803/
- Nakra and colleagues, moisturiser with sunscreen for retinoid irritation, 2026. pubmed.ncbi.nlm.nih.gov/42281708/
- Dhaliwal and colleagues, bakuchiol compared with retinol, 2019. pubmed.ncbi.nlm.nih.gov/29947134/
- Puyana and colleagues, bakuchiol review, 2022. pubmed.ncbi.nlm.nih.gov/36176207/
- Draelos and colleagues, bakuchiol for sensitive skin, 2020. pubmed.ncbi.nlm.nih.gov/33346506/
- Stein Gold and colleagues, adapalene and benzoyl peroxide in one gel, 2022. pubmed.ncbi.nlm.nih.gov/34674160/
- Callender and colleagues, adapalene and benzoyl peroxide gel results, 2025. pubmed.ncbi.nlm.nih.gov/40122140/
- Andres and colleagues, adapalene and benzoyl peroxide tolerability, 2008. pubmed.ncbi.nlm.nih.gov/18441854/
- Dubina and Fleischer, dapsone and benzoyl peroxide orange staining, 2009. pubmed.ncbi.nlm.nih.gov/19770443/
This guide is general information, not medical advice. If you’re pregnant, on prescription skincare or have a skin condition, check with your doctor or pharmacist.
