Zinc oxide - Non-nano, noncoated
Non-nano Zinc oxide effectively and safely blocks both UVA and UVB sunrays and is far superior to the chemical sunblocks (see chart below). A naturally occurring element in the Earth's crust, it forms a physical barrier on the skin.
While UVB makes up only 5-10% of solar radiation, its high energy damages surface epidermal layers and causes sunburn. UVA penetrates deeper layers of skin and causes tanning. However, both types of UV rays can cause skin cancer because they damage skin cells and can alter their DNA. Both types of rays also contribute to premature aging of skin.
The SPF scale is not linear: SPF 15 blocks 93% of UV rays, SPF 30 blocks 97% and SPF 50 98%.
We add zinc oxide to some of our lip balms to give them natural sun protecting properties. We only use non-nano zinc (comprising of particles larger than 0.1um) which prevents it from being absorbed - if some does get in your mouth through the lip balm, it passes through without entering the system.