Solar ultra violet radiations (UVR) is divided into three categories of rays:
1. UVC (200-280 nm);
2. UVB (280-320 nm); and
3. UVA (320-400 nm).
UVC is the most biologically damaging radiation, but, fortunately, it is filtered out by the ozone layer.
So, here on Earth, we have mainly UVA and UVB radiation.
UVB sticks mainly in the upper layers of the epidermis and causes visible sunburn. This radiation accounts only for about 5% of UV radiation.
UVA penetrates deep into the skin and causes serious and longterm damages, its responsible for skin cancer; along with that, it doesn`t cause skin burns.
This radiation accounts for about 95% of UV radiation.
Many studies demonstrate that some botanical oils, such as shea butter, olive oil, or coconut oil, give very light protection and ONLY against UVB rays.
No botanicals provide sufficient and wide-spectrum UVR protection.
References:
- Alberts,B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P., (2002). Molecular Biology of the Cell.
- Chanchal D.K., and Swamlata S. (2010). Pharmacognosy Res., Jan-Feb; 2(1): 22–25.
In vitro sun protection factor determination of herbal oils used in cosmetics.
- Moyal, D. (2008). How to measure UVA protection afforded by sunscreen products. Expert Review of Dermatology, 3(3), 307-315.
- Wang, H.T., Choi, B., Tang, M.S. (2010). Melanocytes are deficient in repair of oxidative DNA damage and UV-induced photoproducts. Proceedings of the National Academy of Sciences, 107(27), 12180-12185.