A Guide to Skincare Layering
Layering your skincare can be confusing, so we asked Cosmetic Chemist Lalita Iyer to clear up the facts on how to layer your skincare products, if wait times matter, and ingredients that you can and cannot combine together.
Let’s begin by first understanding the structure of the skin
The skin’s uppermost layer is known as the stratum corneum which consists of about 10-25 rows of dead keratinocytes (also known as corneocytes) embedded in something known as the lipid matrix. The stratum corneum is essentially an excellent barrier which defends your skin against outside aggressors. Through the proper use of skincare products and a dedicated routine, you can help reinforce and maintain a strong skin barrier.
How to layer your skincare
An easy rule of thumb to layer your skincare is to go from your thinnest to thickest product. This would mean that after cleansing your face, you would use your water-based products such as toners or serums, then your oil-based products such as a thick moisturiser or oil. The idea here is that water-based products should go on before oil-based products. Using occlusives such as oils at the end of your routine will help to seal in moisture in your skin.
Additionally, hydration of the stratum corneum (top layer of the skin) has been shown to make the skin more permeable. This can be achieved by using products with a high water content first such as an essence or a mist. Water is a great penetration enhancer for your skin which means it can help the next few products to sink into your skin well, especially if you’re using treatment products that contain actives. However, keep in mind that this also means a potential increase in irritation for those with sensitive skin.
What you can and cannot layer
Layering skincare products has been a confusing topic, however, there hasn't been any real research on this topic. From a chemist's perspective, any acidic products such as alpha hydroxy acids, beta hydroxy acids and vitamin C can be layered in the same routine as they all work at a low pH. Retinoids can also be layered with AHAs, BHAs or any other actives such as arbutin, kojic acid, and tranexamic acid to name a few. However, keep in mind that layering too many actives in one routine can increase irritation, especially if you have sensitive skin. If that's the case, it's best to use actives at separate times or on alternate days. For example, you could use an AHA such as a lactic acid exfoliant during the day, and a retinoid at night.
One interesting fact is that advancements in skincare technology have allowed multiple actives in the same formulation, where each active plays its respective role. If you find a product that has multiple actives in the same product, you can just use that one product, as long as you don’t experience any irritation.
In general, wait times aren't all too important and there hasn't been any real research on this topic. There are a few general guidelines one can follow if you'd like, however, these aren't hard and fast rules.
When using a treatment product such as salicylic acid or benzoyl peroxide, you could wait a few minutes for the active ingredient to soak into your skin before following up with the rest of your skincare routine such as using a moisturiser.
As an industry, we generally recommend that retinoids are applied on dry skin to avoid irritation, however, if you are an experienced user of retinoids and your skin is acclimatized, applying retinoids to damp skin can help penetration.
For anything else such as layering niacinamide serums with AHAs or BHAs, wait times don't make much of a difference and results will likely be the same. One tip to keep in mind is that using actives on damp skin can increase irritation because water makes the skin more permeable. So, it is best to wait for your skin to dry before using your actives, especially if you have easily irritated or sensitive skin.
Ingredients you should and should not mix
There are no hard and fast rules on what you can and cannot mix because formulation and delivery systems play a huge role. The only ingredient combination you should not mix is benzoyl peroxide and retinoids, due to the fact that benzoyl peroxide produces oxygen which can cause the degradation of retinoids.
There are also many ingredients that actually work well together and chemists are encouraged to formulate them together into a product. For example, niacinamide and salicylic acid can both work together to reduce sebum and decrease the appearance of pores, and niacinamide also strengthens your skin barrier.
Retinoids and AHAs/BHAs can be used with hyaluronic acid because hyaluronic acid is a humectant that functions to decrease any risk associated with retinoids. Vitamin C, vitamin E and ferulic acid, generally found in the same product, act as powerful antioxidants by fighting free radicals and helping to stimulate collagen. Brightening ingredients such as kojic acid, arbutin, and tranexamic acid can also be used together to tackle dark spots.
Finally, it’s important to note that many of these skincare tips may work for some and may not work for others. It’s best to always listen to your skin and do what works best for your skin type and specific skin condition.
Words by Lalita Iyer, Cosmetic Chemist
Qualifications - Bachelors in Chemistry and Masters in Biotechnology
Follow Lalita @skinchemy