These Skincare Ingredients Should Never Mix

Woman applying face cream in front of mirror
Rate this post

Layering skin care products is common – after all, this enables your skin to really gain the most out of your skin care routine. Usually, this is not too much of a problem. While each product does contain its own special blend of ingredients, each product you use will often support the next, helping to give your skin all it needs. 

However, it isn’t always this easy…

Certain active ingredients can sometimes counteract each other, while other combinations can actually end up damaging your skin. 

Don’t worry, so long as you know which skin care ingredients should never mix, you will still be able to layer your skin care products to create an effective skin care routine. 

Vitamin A and Vitamin C

Both vitamin A and vitamin C are ingredients that are often recommended when it comes to targeting a wide range of skin care products. They are both very powerful vitamins, which is why many think that their effects will be doubled when they are used together. 

However, this isn’t true at all…

Different ingredients work best at different pH levels, and this applies to both vitamins A and C: 

  • Vitamin A – works best at a pH of 5.5 to 6
  • Vitamin C – works best at a pH lower than 3.5 

Wondering what happens when these two ingredients are used together? 

It does not damage your skin in any way, but it will likely cause the vitamin C to become inactive, meaning that it would not have much of an effect on your skin. 

Of course, these are still both amazing ingredients to use on your skin, so long as you use them separately. 

When should you use each one? 

Save vitamin C for morning use. 

Why? 

Because vitamin C is great at giving your skin some addition sun protecting benefits. It will also enhance the way in which your sunscreen works, making this a fantastic ingredient to wear underneath a sunscreen. 

On the other hand, the sun can deactivate vitamin A, no matter which form of the vitamin you go for. Plus, vitamin A is also very effective at supporting the skin’s functions at night, from collagen production to skin cell regeneration, making this an ingredient best saved for the evening. 

Vitamin A and AHA’s/BHA’s

AHA stands for alpha hydroxy acid, while BHA means beta hydroxy acid. Both of these are forms of chemical exfoliants – they work by dissolving away the glue-like bond that causes dead skin cells to adhere to the skin, enabling those old and rough cells to be cleared away. 

There are several AHAs out there, such as: 

  • Glycolic acid 
  • Lactic acid 
  • Malic acid 
  • Citric acid

On the other hand, there is only really one BHA, and this is salicylic acid. 

So, why shouldn’t you combine any of these acids with vitamin A? 

As mentioned above, those acids all exfoliate the skin. 

Well, vitamin A does this to some extent too. Although it does not break down those dead skin cells on the surface of the skin in the same way that the acids do, it stimulates the skin cell turnover process from a deeper level. This is the rate at which your skin naturally sheds its dead skin cells in order to replace them with the fresh new ones that it has created. 

Infographic showing dermis and epidermis of skin Exfoliation does this too, meaning that you could end up with skin that is really irritated, and also red and dry. There are also a few skin conditions that can arise when the skin sheds its skin cells too quickly, such as psoriasis. 

Don’t worry, you don’t have to give one of those ingredients up…

Instead, simply use those ingredients at different times of the day. You could also use them on different days completely, especially since most chemical exfoliants only need to be used a couple of times a week. All you need to do is give your vitamin A products a miss on those days, swapping them with something else instead. 

Vitamin C and AHAs/BHAs 

Just like vitamin A, vitamin C is another ingredient that you should not be using alongside hydroxy acids. 

Why? 

Although vitamin C is an extremely powerful antioxidant, it is also quite an unstable ingredient. 

As you know from above, vitamin C needs a very particular pH level in order for it to be effective. Hydroxy acids will quickly throw this off-balance, making your vitamin C almost worthless. 

Plus, you will notice that vitamin C is usually listed as L-ascorbic acid on an ingredients list. This tells you that vitamin C is an acid itself, meaning that combining it with another acid could be highly irritating and drying for your skin. 

Either skip the vitamin C on the days that you are going to be using a hydroxy acid, or make sure that you use them both at different times of the day. 

Vitamin A and Benzoyl Peroxide 

You are probably sick of seeing vitamin A being mentioned on this list…

Well, this will be its last mention, and this time it is related to combining vitamin A with benzoyl peroxide. 

If you regularly deal with acne, then benzoyl peroxide is probably an ingredient that you are extremely familiar with. 

It is a popular acne treatment that works in a couple of ways: 

  • It destroys any acne-causing bacteria, both on the surface of the skin as well as within the pores 
  • It dries out the skin, meaning that excess oils are not able to clog up the pores and trigger breakouts 

Of course, vitamin A is often recommended as an acne treatment too…

It keeps the pores clear while also regulating oil production. 

When these two ingredients are used in the fight against acne, they have been proven to be even more effective than antibiotics, making it no surprise that this combination is becoming increasingly popular. 

However, while they are both effective acne-fighting ingredients, they shouldn’t be mixed. 

Why should vitamin A not be mixed with benzoyl peroxide? 

Because the two ingredients actually deactivate each other, meaning that neither of them will have an effect on your acne. 

Just like with the other ingredient pairings on this list, you would be best off using them at different times of the day. 

Benzoyl Peroxide and Hydroquinone 

Woman applying face cream in front of mirror

You now know that benzoyl peroxide should not be used with any form of vitamin A, but did you know that this is an ingredient that should also not be used with hydroquinone? 

Hydroquinone is a skin lightening ingredient that targets dark spots and pigmentation. 

Although it is a potent ingredient with a few side effects, it is a relatively safe one, so long as it is not combined with benzoyl peroxide.

What’s the problem with combining hydroquinone and benzoyl peroxide? 

It can result in skin staining. Although these effects are only temporary, and can usually be washed away, this is still something you want to avoid. 

Those who would be using both ingredients together are likely to be dealing with acne, since benzoyl peroxide is an acne-fighting ingredient and hydroquinone can prevent and lighten acne scars. 

You can still use both of these ingredients on your skin, so long as you use them in different areas. For example, use the benzoyl peroxide on the areas where you are experiencing breakouts. You can then use the hydroquinone directly on any scars you may have, so long as these are not the same areas in which the benzoyl peroxide was applied. 

Benzoyl Peroxide and Vitamin C 

Wondering why benzoyl peroxide has appeared so many times on this list? 

Because it is such a powerful ingredient, meaning that it can have unwanted effects on some of the weaker ingredients out there. 

Ok, so vitamin C isn’t exactly a weak ingredient, but, as mentioned earlier, it is very hard to keep this vitamin stabilized. When you combine it with benzoyl peroxide, you have no hope at all of doing so.

However, theoretically, these two ingredients should work well together. After all, benzoyl peroxide helps to treat and reduce acne, while vitamin C helps the skin to heal, while providing brightening and scar-lightening properties. 

What actually happens when vitamin C is mixed with benzoyl peroxide? 

The benzoyl peroxide has an oxidizing effect on the vitamin C. This not only prevents it from working properly, but can also lead to the formation of free radicals in the skin. This is something that you definitely do not want, as this will only severely damage your skin cells in the long run, resulting in premature skin aging. 

You would experience much better results if you were to use each of these ingredients at different times of the day. 

If you really need to use them both at the same time…

Make sure that you wait a few minutes in between applying each ingredient, as this will prevent them from mixing together quite as much. You should also make sure that the concentration of benzoyl peroxide you are using is not too high – the higher the concentration, the more it will interfere with the vitamin C. 

Octinoxate and Avobenzone

There are two types of sunscreens out there: 

  • Physical sunscreens – these use minerals, such as titanium dioxide and zinc oxide, to reflect UV rays away from the surface of the skin 
  • Chemical sunscreens – these use certain chemicals, such as octinoxate and avobenzone, to absorb the sun’s UV rays, before converting them into heat and emitting them from the body 

Infographic showing the difference between physical and chemical sunscreens

Both octinoxate and avobenzone are effective chemical sunscreens. In fact, you will often find both of them used in a sunscreen formula, usually alongside a few other sun-protecting ingredients, such as octisalate, oxybenzone and homosalate. 

Why can’t a sunscreen contain just one sun-protecting chemical? 

Because, when used at a high concentration, those chemicals can be extremely irritating to the skin. In order to avoid this, sunscreen manufacturers combine multiple sun-protecting chemicals at a lower concentration. Together, they provide the SPF figure stated on the bottle, without causing too much irritation to the skin. 

Although combining sunscreen chemicals is common practice, two of those ingredients that should never be combined are oxtinoxate and avobenzone. 

Why? 

Because the two of them basically deactivate each other. 

Interestingly, this reaction does not take place in the bottle – it only happens once these two combined ingredients have been exposed to the sun.

You are probably wondering…

If the two ingredients render each other less effective, why are they both commonly used together in sunscreens? 

There are a few possibilities behind this…

One reason would be that avobenzone is the only chemical filter out there that absorbs the widest spectrum of UVA rays. On the other hand, octinoxate is the most effective chemical filter for absorbing UVB rays. Combining them together is the easiest way to create a sunscreen, and it is also the most cost-effective method too. 

Some sunscreens do also contain octocrylene, which helps to keep both avobenzone and octinoxate more stable. Although the ingredients still deactivate each other, this does not happen to quite the same extent when octocrylene is involved. 

Still, for a sunscreen to be as effective as possible, it should never contain both avobenzone and octinoxate. Although many sunscreens do contain both, there are also numerous others that contain just one of the two – just make sure that you check the ingredients list before purchasing one. 

You also have the option of going for a physical sunscreen instead, as these will not use either of the above chemicals. There have been some concerns lately relating to the safety of chemical sunscreens, so you may be better off anyway going with a physical version. 

There’s nothing wrong with having shelves full of skin care products, so long as you are using the correct combinations together. By avoiding the pairings listed above, you will be able to prevent any unwanted skin reactions and ensure that your skin care products are bringing your skin maximum benefits.