We make a variety of hand crafted products and one of our soaps is made with Shea butter, cocoa butter, palm oil, olive oil, tea tree, lavender, and calendula. I am wondering if you might know how deep into the skin soap penetrates on average?
One of our clients/friends has a rare condition that causes chronic wounds to appear and as soon as she started to use the soap her wounds began healing amazingly fast, she plans to share this soap with her doctor and it got me wondering about how deep into her skin the Tea tree, Lavender, Calendula might be reaching.
I know that according to the PDR for herbal medicine tea tree, lavender, and calendula have shown tissue regeneration and antimicrobial action in studies, thats why I combined them, but I am having trouble finding information on the depth of skin penetration that soap reaches.
Soap and Skin Care
Handcrafted cold processed soap has a lot of benefits over the so called soap bars that are mass produced. Handcrafted soap typically contains a good amount of oils that soften the skin as well as glycerin which helps hold moisture to the skin. Your soap like many people’s hand crafted soap contains nice oils including shea. Shea is rich in vitamins such as A and E. Vitamin A is important in skin care. It promotes cell division and so increases the rate of epithelial turnover. This alone can help to thicken and repair skin. Calendula added to your soap is also rich in vitamin A. So I don’t know if it is so much about penetration of your essential oils but rather the soothing effects that handcrafted soap in general has on the skin.
There are a number of factors to consider in addressing this question:
* “Wash-off” products are only only the skin for short periods of time compared to “leave-on” products, so dermal penetration is also comparatively low, in spite of the fact that soaps and shampoos penetrate skin quite well.
* You can’t really talk about the skin absorption of soap, since it’s not a single substance, and the skin is selective about what it lets through.
* One product ingredient can influence the skin penetration of another, so predicting the dermal absorption of a mixture such as soap is tricky.
Even with essential oils, dermatologists study the skin absorption of individual constituents, not the whole oil, again because of skin selectivity. Some of the constituents of tea tree oil, for example, penetrate skin only very poorly, although lavender oil constituents generally absorb well.
The essential oil constituents are are well absorbed, pass through the stratum corneum (surface layer of dead cells) into the “viable epidermis”, past the dermo-epidermal junction, and into the dermis, and then the blood capillaries. So they go as far as it’s possible to go.
Fatty oils, such as palm oil and olive oil, consist of molecules that are somewhat larger than essential oil constituents, and they are also more “fatty”. Both of these factors make it less easy for them to pass through the various skin layers, and evidence suggests that they generally may make it as far as the viable epidermis, but no further. Having said that, the presence of essential oils can assist the penetration of fatty oils.