Can you mix glycolic and salicylic acid

We all know oil and water don't mix—but did you know Vitamin C and retinol together are a literal recipe for disaster?

07.09.2022 by Addison Aloian

@haileybieber

It’s basic high school-level science: oil and water don’t mix. In fact, oil actually repels water, so when it comes to your skincare, using an oil-based product will leave a film on your skin which prevents water-based formulas from absorbing. If you want to use both formulas in the same routine, apply your water-based products first, and oil-based products on top. 

When it comes to skincare acids, the good news is that (when used correctly) they can deliver phenomenal results. We're talking about an other-worldly glow where skin looks so luminous it can outdo any IG filter.

There's more too. Not only can they do a number on dullness, but acids also go to town on eradicating acne scars, fines lines, pigmentation, breakouts and blackheads. In short, there ain't much they can't do.

Now, for the not-so-good news. They can be notoriously tricky to use correctly, which can result in some serious irritation. We're not talking about Samantha Jones's chemical peel level of irritation, but still, there are rules to live by before dousing your face in glycolic acid or going ham with the PHAs.

Here to reveal the do and don'ts of skincare’s heavy hitters is WH Skin Deep columnist and founder of SKNDOCTOR Dr Ewoma Ukeleghe.

But first... what are the best acids for skin?

There are fifteen acids that most dermatologists rate and thankfully you don’t need a degree in chemistry to get your head around them. Here are the top ones that should form the backbone of your skincare regime.

AHAs

AHAs such as glycolic, lactic and mandelic interact with water molecules in the upper layers of the skin, which triggers a keratolytic (exfoliating) effect. The interaction between water and AHA dissolves the glue-like bonds that hold dead cells to the surface of your skin and allow other products to penetrate more effectively.

Glycolic is the best acid for fine lines

Studies show that glycolic acid helps to initiate collagen synthesis and boost hyaluronic acid (more on which later) in the lower skin layers, plumping fine lines and wrinkles. However glycolic acid is so ruthlessly efficient that it only takes one application to yield results.

The downside? It works so quickly that skin can become irritated. This is where percentages come in – the higher the strength, the more likely irritation will occur.

Lactic acid is the best acid for dry skin

Created synthetically in a lab, this AHA is gaining a following because its molecules are bigger than those in glycolic, so don’t penetrate as deeply to trigger that peeling action.

If you have dry or sensitive skin, this is a good thing. At low percentages, around 5%, lactic acid also acts as a humectant, drawing moisture into the skin while it exfoliates.

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Mandelic acid is the best acid for pigmentation

This is the newest AHA on the block. Research published in Dermatologic Surgery showed that it was as effective as glycolic at treating pigmentation from sun damage, but with less redness and irritation. And further studies show that it also reduces melasma by as much as 50% in four weeks.

Mandelic’s molecules are twice the size of glycolic’s and a third bigger than lactic’s, so irritation is reduced, as it takes a long time to penetrate the skin. But don’t be fooled by its softly-softly approach. Like other AHAs, mandelic’s micro-exfoliating properties help lift excess pigment from the skin’s surface.

However, it’s the only AHA to work in the skin’s deeper layers to inhibit melanin production. So what it might lack in speed, it makes up for in depth.

Mandelic Pigmentation Corrector Night Serum

Allies of Skin cultbeauty.co.uk

Medik8 Pore Cleanse Gel Intense

By Wishtrend Mandelic Acid 5% Skin Prep Water

BHAs

Salicylic acid is hands down the best acid for oily skin and acne

Unlike AHAs, salicylic oil-soluble, meaning it can cut through excess oil on the skin’s surface. It’s basically the only acid able to infiltrate the pore lining, so it can then flush out dirt, dead cells and trapped sebum. This quickly restores oil flow out of the pore, so it’s less likely to get clogged with the debris that leads to blackheads, whiteheads and acne.

salicylic acids

Clear Extra Strength 2% BHA Exfoliant

EradiKate Salicylic Acid Blemish Spot Treatment

Kate Somerville spacenk.com.uk

The Ordinary Salicylic Acid 2% Masque 50ml

The Ordinary lookfantastic.com

Malin + Goetz spacenk.com.uk

Which acid is best for glowing skin?

All of them will be able to banish dull skin with ease, so it really depends on what other issues you're trying to tackle, in which case it just comes down to preference.

Retinoic acid is highly regarded as the holy grail thanks to its can do attitude. It's only available via prescription but there are lots of retinol based products available over the counter or online.

THE INKEY LIST Retinol Serum

THE INKEY LIST cultbeauty.co.uk

A+ High-Dose Retinoid Serum

Sunday Riley cultbeauty.co.uk

La Roche-Posay Redermic [R] Retinol Eye Cream 15ml

La Roche-Posay lookfantastic.com

Medik8 Crystal Retinal 3 30ml

10 ways your using acids wrong

1. Overdoing it with application

'Enthusiastic over-exfoliation can be counterproductive to the health of your skin. For particularly sensitive skin, I would say to be careful with your application of stronger acids such as glycolic and salicylic as these can cause further redness and irritation by damaging your skin’s moisture barrier,'explains Dr Ukeleghe.

2. Not following with SPF

'This is always essential but even more of a non-negotiable when you are using actives like Alpha Hydroxy Acids. Using AHA’s minimises your ‘natural’ sun protection by thinning your top layer, it leaves you more susceptible to sun damage. I always apply SPF as my last step in my routine,' she clarifies.

Anti-Wrinkle Face Suncare SPF50

Play Everyday Lotion SPF 50 with Sunflower Extract

Supergoop! cultbeauty.co.uk

THE INKEY LIST cultbeauty.co.uk

City Skin Age Defense Broad Spectrum SPF 50

3. Applying acids every day

'With AHA’s I like to take the attitude of less is more - especially at the beginning. Start slowly by applying once every couple of days as part of your nighttime routine to not irritate your skin,' says Dr Ukleghe.

'Then you build up but be sure to give your skin regular breaks. So, use one bottle of product, then have a month off,’ she adds.

Glycolic Acid 7% Toning Solution

The Ordinary cultbeauty.co.uk

Nip+Fab Glycolic Fix Liquid Glow 6% Cleansing Lotion 100ml

The Shortcut Overnight Facial Peel

4. Cocktailing acids with actives

'Be careful with cocktails of active ingredients- overloading your skin with actives like retinols, potent antioxidants and acids will again be counterproductive for the health of your skin, resulting in an imbalance and ultimately causing breakouts and sensitivity.'

'So avoid applying a lactic serum after a glycolic toner as this will be instantly irritating to the skin and cause redness. Similarly, save your vitamin C for the days you haven’t applied AHA’s,' she adds.

5. Not following brand instructions

'It's so important to properly read the instructions. If it’s an acid-based mask check how long it should be left on for and follow this guidance properly to avoid causing any damage to your skin’s hydrolipidic barrier,' Dr Ukeleghe.

'Whilst it might be tempting to pack on your newest product; remember they ARE an active ingredient and can cause harm if they are used incorrectly,' she adds.

6. Treating all acids equally

'It’s also really important not to be scared of all acids; so ingredients like hyaluronic acid for example tend to suit most, if not all skin types, and are essential for keeping your skin adequately hydrated and plumped,' says Dr Ukeleghe.

7. Thinking you can't use AHA’S and BHA’s together

'In fact these two work really well with one another, for instance, oiler skins would work well with a salicylic acid cleanser followed by a glycolic toner,' reveals Dr Ukeleghe.

'The salicylic acid will work to penetrate the pore of the skin. Alpha-Hydroxy Acids are water-soluble so whilst they work well to loosen dead skin cells, BHA’s like salicylic acid penetrate lipid layers more easily so work deeper to unclog pores.'

8. Forget the mindset that if a product tingles or hurts it’s working

'This myth is particularly common. In my opinion, your daily skincare shouldn't be painful, a slight tingling sensation from a salicylic acid-based product or mask shouldn’t be too much to worry about, but in general avoid anything that leaves you red, sensitive or massively tingly. Know when to stop, If your skin is irritated, give it a break,' explains Dr Ukeleghe.

What should you not mix glycolic acid with?

What should you not combine with salicylic acid?

Which is stronger glycolic or salicylic acid?

Can I use salicylic acid in the morning and glycolic acid at night?