How cosmetic ingredients penetrate the skin
Y'all, there are so many misleading Tweets and articles about how cosmetic ingredients penetrate the skin I just had to talk about it.
"Our skin absorbs X kilos of cosmetics each year."
"Every thing applied on our skin is absorbed in the blood stream within X seconds."
"X ingredient in that lotion is absorbed and causes cancer."
It's not that simple. If it was, we would all become wet sponges when we took a shower or a swim. Let's stop and do our research before sharing this pseudoscience. Abeg.
Our skin is smart
For real. It's designed to keep harmful stuff out and the good stuff in. And it does it's job well thanks to the structure.
It has three layers: the epidermis, the dermis and the fat layer or hypodermis.
A cosmetic ingredient would have to penetrate through all of that before being absorbed in the blood stream. Cosmetic formulas are designed to keep ingredients away from the blood stream.
When the ingredient is penetrating the skin, it hasn't been absorbed by the body and can't affect it yet. It just penetrates through the upper layers of skin, does it's job and will eventually be removed as part of the dead skin cells.
Our bodies are smart too
If it can actually get through to the bloodstream, then it's absorbed. Our body filters toxins that happen to wander into our blood stream.
Low levels of toxins are expelled through urine and faeces regularly. If not expelled, then they can cause issues that range from allergic reactions to toxicity.
Factors that determine how far a cosmetic ingredient can go
Our skin naturally produces oils and lipids so oil soluble ingredients like salicylic acid find it easier to penetrate than water soluble ingredients like lactic acid.
It's easier for an ingredient to penetrate thin skin e.g. the lips and harder for it to penetrate thick skin e.g. the soles of the feet.
This refers to how much of an active is required to make a difference in the skin. For example tretinoin from 0.025% -1.0% will increase collagen production.
Our skin is built like a brick wall. The dead skin cells are bricks surround by (mortar) lipids. This keeps the skin intact. Not much can get through this.
If a cosmetic ingredients is too large to slip between the skin cells or 'bricks' then it simply won't penetrate e.g. collagen. But then again, not all ingredients need to penetrate the skin to be helpful e.g. hyaluronic acid. So size isn't that huge a deal.
The next time someone tells you to fling your favorite lotion to the hills because of toxins. Ask them for receipts.
This post has been updated and was previously published on my other beauty blog, Wolf + Moroko