I am sometimes asked whether vitamin A such as retinol and/or hydroxy acids such as glycolic acid thin the skin. The answer is – these ingredients actually THICKEN the (living!) skin, not thinning it.
It’s a common misconception that these ingredients are thinning the skin, but they actually only thin the dead layer of horn cells (corneocytes) on the skin surface, not the living skin. That’s why both retinols and glycolic acid containing skincare products should always be used in conjunction with an SPF30-50.
However, this exfoliation of corneocytes is a good thing, not only because your skin will look less dull and lack-lustre, but also as it signals to the basal cell layer of the epidermis (where our all-important skin stem cells live) to produce more lovely new cells, which means that the living epidermis actually thickens over time (and also consists of a healthier, ‘younger’ epidermis).
Retinol has even been shown to not only thicken the epidermis (the outer layer of our skin), but also the dermis (the deeper layer, there our collagen and elastin live). Only when retinol is misused, there may be a risk of damaging the skin’s barrier function and causing potential issues such as increased water loss, but generally retinol strengthens our skin, is highly beneficial and I recommend everybody from their end 20s onwards to start using a retinol containing product to slow down skin ageing on a cellular level! I do it myself…