Which skincare ingredients are dangerous to mix?

Different products offer different promises to your skin – but this does not mean that using all of these formulas at once will give your skin the balanced nourishment that it needs.

In fact, it could do quite the opposite and cause some serious harm to your skin. To help you understand whether your skin routine could be helping or hindering your skin, Lisa de-la-Plain at Beauty Flash has put together a guide on which ingredients work harmoniously together or not.


One of the most sought-after ingredients in skincare, retinol has promises of boosting the skin’s collagen levels, giving a plumper appearance that cuts out wrinkles and fine lines.

The only catch, it can be extremely irritating and exacerbate skin dryness and other ingredients can promote this, such as AHA/BHA acids.

I would also recommend not using benzoyl peroxide as well as retinol as they cancel each other out rendering them less effective.

With retinol, you should make sure you’re using moisturising ingredients like hyaluronic acid, which can be found in Medik8’s Advanced Night Restore. It’s specifically designed to be used after using retinol to moisturise the skin.

It’s also worth noting retinol can make you extra sensitive to the sun, so it’s vital you wear SPF every day when using this ingredient.

Vitamin C

Vitamin C is another star ingredient. Used to protect the skin from oxidative free radical damage and reduce redness and evens out the skin tone, it’s best used in the daytime.

As it’s effectively an acid, avoid mixing vitamin C with AHA/BHA acids such as glycolic or lactic acids.

Vitamin C is also unstable, so any acids you layer it with will destabilise the pH balance and render it completely useless before it can work its magic.

Vitamin C responds well to being mixed with antioxidants, and this Dermalogica Age Smart BioLumin C Serum combines the two to use the skins own defences to brighten and firm.


Basic science but oil and water do not mix. In fact, oil 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.

Make sure you check the label on purchase so you know you’re not going to miss out on the benefits the product can offer.

The skin can be dry or it can be dehydrated and treatment for these two issues are different from one another. Dry skin lacks sebum oil, so it requires oil-based products to calm. Likewise, dehydrated skin is gasping for water to quench its thirst.

Less is more

Always be careful when using acidic based products, they are a strong ingredient, so using too much of it can end up doing more damage than good.

Glycolic and salicylic in particular, shouldn’t be used together. Both have the same objective, acting like an acidic exfoliator, removing dead cells from the skin. When used separately, they’re effective, but together it is just too much for the skin to handle and it will cause peeling.

Moisturising after applying either of these acids is extremely important to limit irritation. Look for products that include ceramides, hyaluronic acid or glycerin such as Medik8’s Daily Radiance Vitamin C SPF 30 to draw moisture into the skin and keep it locked in.


SPF is an everyday essential and should always be incorporated into your skincare. It’s the only way to effectively protect skin from cancer and environmental aggressors, which can lead to premature signs of aging.

SPF works well when layered over any other ingredient so there really is no excuse not to wear it. However, don’t mix your SPF with make up or moisturisers, it should be applied as a single layer, otherwise it could lose some of its protection factors.


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