5 Skincare Ingredients You Should Not Mix

One of the disadvantages of having so many beauty products made easily and cheaply avaliable to us is that you can mix together the wrong ingredients sometimes.

Because, let’s face it, as much we all love the fact that brands like The Ordinary and The Inkey List have brought us isolated, potent ingredients in a bottle that costs £5.99, we are not all cosmetic formulas with the knowledge to mix (or in this case not mix) the right ingredients together.

This is also a question that is searched time and time again on Science and Skincare and so I thought it was time to answer it.

After doing more of my own research via listening to you, asking scientist friends and just generally reading on the topic I’ve put this list together as a kind of cheat sheet.

Bookmark this post and look at it whenever you’re not sure!

So, let’s get started.

Vitamin C and retinol

The major problem between these two are that they are both very powerful ingredients and they both treat similar things like; the signs of ageing, including fine lines, firmness, and uneven skin tone. 

So, when you use these things one after the other it’s almost like amplfying the potency of both of then. This is likely to cause irritation in those with sensitive skin which can lead to breakouts and an overall weakening of the skin barrier.

Alpha hydroxy acids and retinol

Okay, so you know AHA’s like glycolic acid and lactic acid are chemical exfoliants and while technically you can use them with retinol based products if you have sensitive skin it’s best that you don’t use the one right after the other.

You see the problem with pretty much all of these ingredients is that, they are potent. You’re literally using an acid to extract the dead layers of skin from your face. That’s gonna leave you a little vulnerable for a little while.

This doesn’t mean you can’t use these products in the same routine but maybe separate them into your day and night rituals.

Vitamin B3 and alpha hydroxy acids

Vitamin B3, which is another name for niacinamide is a skin conditioning agent that helps repair and refine the skin’s structure. It tends to work best in an environment with a neutral pH.

If you’ve learned anything from my blog you’ll know that AHA’s are low on the pH scale (because they are acids). This means that it brings the pH level of vitamin B3 down.

While that won’t necessarily harm you to use them both together, they basically cancel each other out.

Benzoyl peroxide and retinol

If you’ve spend any amount of time researching how to deal with acne then you will have come across these ingredients. For good reason too because both of these ingredients work to prevent breakouts.

However, what you may not know is that benzoyl peroxide is, although a potent acne product that’s great for inflammatory acne, it can also inactivate a topical retinol.

This doesn’t mean that you cannot use benzoyl peroxide during the same period that you’re using retinol; it just means they should never be layered on top of each other.

Vitamin C and alpha hydroxy acids

Four words.

High levels of acidity.

Ok so generally vitamin c is less acidic than AHA’s. This means if you layer them together the AHA’s bring the acidity of vitamin c further down. That can cause vitamin c to lose its potency.


First conclusion, there is a misconception that if you mix the wrong ingredients together your skin will burn off or something. Usually, you’ll hardly see a reaction (unless your skin is super sensitive) but what will happen is that you waste products because they’re potency is the thing that’s affected.

The second point I’d like to make is this; take your time adding something into your routine and be careful with layering. You don’t have to do it as soon as you buy another product.

Expose your skin to one product at a time. If your skin starts to react badly, you’ll know which product was the most likely culprit.

Any questions just let me know.

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