The skincare ingredients you shouldn’t use together, according to an expert

With the advent of single ingredient-led brands such as The Inkey List and The Ordinary, it’s easier than ever to design for yourself a comprehensive, effective skincare routine that covers all bases. But sometimes, more choice and variety isn’t necessarily a good thing; in fact, it can lead to over-complications, confusion, and even adverse results. 

We all know that our skin benefits from ingredients like vitamin C, hyaluronic acid, retinol, and exfoliating acids, but what is sometimes not clear is which shouldn’t be used alongside one another, particularly in the same morning or evening routine. 

Brands such as The Inkey List — with their ‘Knowledge Is Power’ tagline — have taken it upon themselves to act as educators when it comes to what can and cannot be used together.

However, when it comes to strict rules to follow about which ingredients you absolutely should not use at the same time, there actually are only a select few. ‘Every once in a while, there will be a big buzz online about the ingredients that do not work well together in skincare with lists of ingredients as long as your arm,’ says Jennifer Rock, dermal facialist and founder of Skingredients. ‘In reality, there aren’t as many as you’d think, and even so, they come with plenty of clauses!’

The skincare ingredients you shouldn’t use together

Retinol and exfoliating acids 

What do these ingredients do?

Retinol: Retinol is a derivative of vitamin A, and has been hailed in recent years as the modern anti-ager all skin above the age of 30 (or even of 25 and up) should be reaching for. As well as working to keep skin looking young and fresh, it can also really help with skin that’s prone to breakouts. However, retinol is a rather potent ingredient and one that needs to be built up slowly within a routine. It also makes the skin highly sensitised to the sun, so should always be followed up with SPF in the daytime. 

Exfoliating acids: By now, many of us will be aware that manual, grainy face scrubs are out, and liquid AHAs (alpha hydroxy acids, such as glycolic and lactic acids), BHAs (beta hydroxy acids or salicylic acid), and PHAs (poly hydroxy acids, including lactobionic acid) are very much in. These acids work to exfoliate the skin safely, and while PHAs are best for sensitive skin due to large molecule size, BHAs are ideal for targeting breakouts, and BHAs are perfect for over-all use to slough away dead skin cells for the normal to oily. 

Why can’t you use retinol and exfoliating acids together?

‘Retinol and exfoliating acids both work to increase skin cell turnover,’ explains Jennifer. ‘Using them together at the same time may lead to skin irritation, redness, flakiness, dehydration and could compromise the skin’s protective barrier, doing more harm than good!’ 

Working them both into your routine

This one has a pretty easy solution; simply use your retinol and acids on alternating nights (both are best used in your PM routine due to the fact they increase sun sensitivity, but sill remember to SPF up the following morning). Alternatively, try a different form of retinol, says Jennifer. 

‘My go-to would be to use the fat-form of vitamin A, which has similar effects to retinol without the same potential for irritation. You’ll find this form, retinyl palmitate, in Skingredients Skin Protein, our vitamin A and C serum, which can be used each AM and PM and plays nice with exfoliating acids.’

skincare ingredients you should't use together
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Retinol and vitamin C

What do these ingredients do?

Retinol: see above

Vitamin C: Every skincare routine can benefit from vitamin C. It is packed full of antioxidants that can help protect the skin from free radicals found in outside aggressors such as pollution, and it also targets pigmentation and helps to brighten the complexion overall. However, vitamin C can be an irritant to some skin types, and you have to be careful which form you opt for if you tend to be on the sensitive side. 

Why can’t you use retinol and vitamin C together?

Jennifer says: ‘Using a retinol and a potent vitamin C product together could make each of them less

efficient whilst irritating your skin. Typically, brands use ascorbic acid as the main form of vitamin C, which oxidises quite quickly, and an acid isn’t the most compatible with an alcohol (like in retinol).’ 

Working them both into your routine

Once again, this issue is easily solved by using them in different regimes; vitamin C is great for morning time due to its brightening and protective qualities, while retinol works best in your PM routine as it increases sun sensitivity. 

Alternatively, Jennifer also recommends her Skingredients Skin Protein product, which uses both vitamin C and A (of which retinol is a derivative of) in a compatible way. 

skincare ingredients you should't use together
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Multiple exfoliating acids 

What do these ingredients do?

See above, where the different types of exfoliating acids are explained. 

Why can’t you use them together?

‘Although it’s common to find more than one exfoliating acid in one product (for example, polyhydroxy acid and salicylic acid, or glycolic acid and lactic acid), DIY’ing your own acid blend is very much not advised,’ says Jennifer. 

‘I find that some [of us] do not realise how many different acids we’re using in our routine, between our cleanser, serum, toner, masks and more, and don’t realise this could be the root of skin irritation.’

Working them both into your routine

This one is less about avoiding using more than one single ingredient exfoliating acid, and more about being aware of what’s in each of your steps. For example, some cleansers have salicylic acid (a BHA) in them, so using this product as well as a BHA toner down the line could be too much for your skin. 

‘If a product is formulated with multiple acids, you’re good to go,’ notes Jennifer. However, she says it is advisable to ‘track the acids in each of your products and cut back if your skin is annoyed, tight,

dehydrated or irritated,’ and also to ensure you are giving enough back to your skin in terms of nourishment and hydration (by including ingredients such as squalane, hyaluronic acid, and certain oils). 

And finally, one myth to take note of re oils and water-based products 

Jennifer is keen to point out that the myth you should not use water-based and oil-based ingredients together is just that: a myth. 

‘I’ve seen some say online that water-based and oil-based ingredients are best to be kept separate, but I would be inclined to disagree,’ she says, adding: 

‘For many with more dry or dehydrated skin, I would recommend “sealing” your water-based serums with lipidic ingredients such as plant oils and ceramides, like in Skingredients Skin Good Fats, our moisturising ceramide balm.’

‘Fatty moisturisers work to help lock in moisture, and when our skin’s barrier cannot retain hydration as well as it used to as we age or as weather changes, they become a true asset to a skincare routine.’

Feature by Rebecca Fearn