This is a super common skincare worry - should I be using this serum with this moisturiser? Can I use these skincare products together? Most skincare ingredients work together to give you skin love but there are some which fight against each other OR even react together to make something that could irritate your skin. Here are the KEY skincare ingredient combinations you should avoid.

Skincare Ingredients You Should Never Mix

In Being Savvy at Skincare by Cheryl Woodman MChem3 Comments

Being a skincare scientist is like being a chef to skin. Really. Skincare science is just a different kind of nutrition, one that your skin drinks up. Just don’t try it the other way around eh, spaghetti bolognese is not easily applied. Skincare science is all about knowing which ingredients are a match made in heaven [1+1 = 3], which work against each other and which ingredients just plain cancel each other out.

This is something I know a lot of you worry about. After putting effort into pampering your skin, you want to know it’s working. You want to know you’ve set up the perfect stage for your skincare to perform. Encore.

What I have for you today will be super helpful in relieving your worry about mixing the wrong skincare. Here my friend is a list of the skincare ingredients you should never, ever mix.

This is a super common skincare worry - should I be using this serum with this moisturiser? Can I use these skincare products together? Most skincare ingredients work together to give you skin love but there are some which fight against each other OR even react together to make something that could irritate your skin. Here are the KEY skincare ingredient combinations you should avoid.

Retinol [vitamin A] & Acidic Ingredients

Heck, what does all that mumbo jumbo mean? Here’s the deal, simply don’t use vitamin A products [also known as retinol] with any kind of acidic ingredients, the key ones being – AHA’s (glycolic, lactic acid), BHA’s (salicylic acid) and vitamin C (as ascorbic acid).

What’s going on here then eh? There are 2 reasons why this mix is like ‘cheffing-up’ a chocolate and apple cider vinegar dessert.

First, they all encourage your skin to exfoliate. This is a key reason why you should not be using Retinol & AHA’s/BHA’s together on the same night. It’s like turning your garden sprinkler from hydrated lawn to power hose mode. Your skin cells and your protective skin barrier are both getting power hosed away. When you’re using skincare ingredients that have a very similar function, together, it’s like asking for trouble. Imagine (well actually I can just remember this… oh dear…) cutting your fringe, realising its wonky and then cutting it again.

Using too many exfoliating products together is going to leave your skin irritated, reddened, flaky and sensitive. Especially to light. And even more especially to UV light. Light is going to increase the skin sensitivity you experience from this ingredient mix.

Secondly, Retinol & Vitamin C just don’t work well together. They’re clunky. Retinol and vitamin C used together are a bit like a sweet & sour mix with relationship tension.

This is what happens when you use retinol and vitamin C together. Retinol is sweet and works best at a pH of 5.5-6, vitamin C is sour and works its best at a pH of <3.5.

Using them together means neither have their perfect skincare stage for a winning performance.

The exception: There’s always one that likes to be a different eh. There are new technologies that will help ingredients to slowly release in your skin. Usually, this is by putting a little jacket on and active ingredient conflict i.e. on vitamin A. This is called microencapsulation and means while vitamin C gets to work straight away at it’s ideal pH level, retinol waits till its safe to come out. Till your skin has balanced back to a normal retinol friendly pH. Then those little jackets get un-zipped.

Meaning if you have a product that contains retinol + vitamin C in the same bottle and it claims something like time-released retinol it should work just fine.

Which retinol are you using? Still looking? Need my help to choose? And to make sure your skincare routine is mixed the right way to get you makeupless skin you love? I’m here to help.

Recap: skincare ingredients you should never mix.

Retinol + AHA’s/BHA’s OR Retinol + Vitamin C

Want a reminder of this? I don’t blame you. It’s why I’ve created this free downloadable, How to Cocktail Your Skincare Like a Pro guide. Just click here, or below to download it now.

Niacinamide & Acidic Ingredients

It’s the same rule as above, just switch retinol for niacinamide. Don’t mix niacinamide with acidic skincare ingredients like AHA’s/BHA’s and vitamin C.

Vitamin C is pretty darn famous in skincare, but you might not have heard of niacinamide. If you haven’t then consider me handing you a skincare present. Niacinamide is a Mary Poppins bag of goodness for skin. It’s multi-tasking anti-ageing with skin brightening, soothing with redness-reducing and spot fighting with oil balancing. Niacinamide is not just a superheroine, it has enough power to be a whole team of superheroines.

Niacinamide and vitamin C are two skincare ingredients with powerful benefits for skin.

It’s just together [when vitamin C is found as L-ascorbic acid] they’re not the perfect pair. There are two things going on here.

First is like mixing paint. Do you have one of those childhood memories? You know the ones. You wanted to mix that special colour and it ended up brown. Brown when you were going for lilac – how has this happened? You try to lighten it back out, mixing in more and more white, and before you know it you’ve manufactured a litre worth of still brown and just not budging.

Now imagine niacinamide as a lovely bright green and vitamin C as a vibrant skin-loving orange. Both look fantastic separately but when mixed together – brown.

Niacinamide and vitamin C don’t work well together in skincare because when mixed together they metaphorically make brown and you can’t un-mix them again to get their awesome skin benefits. Mixed together they can become inactive.

Secondly, niacinamide and acidic skincare ingredients have some chemistry going on ;). Literal chemistry. It’s like when you add flour and yeast together, heat it and you’ve made bread. Well, when you get niacinamide and an acidic skincare ingredient together, they ‘cook’ and niacinamide becomes another ingredient called niacin. This bad boy causes redness and flushing. Yikes.

Pro-tip: Leave at least 20-30 minutes between these skincare ingredients. Or my ultimate recommendation – keep niacinamide for your morning skincare routine and the acidic ingredients that can make skin photosensitive for your pre-bed skincare.

Which niacinamide containing skincare products are you using? Do you need help choosing? If you’re starting to notice things (fine lines, pores, pigmentation), and want to get your skincare routine working it’s butt off for your skin concerns – I’m here for you.

Recap: skincare ingredients you should never mix.

 Niacinamide + AHA’s/BHA’s OR Niacinamide + Vitamin C

With these rules memorised your skincare stage will be perfectly set for its best performance yet. And remember, it doesn’t have to mean you ban certain skincare ingredients from your skin’s diet. Just separate them out into your morning and night-time skincare routine. Skin can get the best of both worlds, so long as you’re super savvy about timing.


Have more questions about how to mix your skincare like a pro? Ask me them here. And if you have a friend who loves skincare but is afraid she’s doing it wrong, use that big green button below to share this blog with love. You are the best.