Understanding the active ingredients in sunscreen is a bit like learning a foreign language that uses a different alphabet. Suffice it to say in short that sunscreens are made up of a combination of two types of ingredients: those that reflect ultraviolet (UV) rays and those that absorb UV rays. Although that might sound simple enough, there are also two types of rays: UVA rays and UVB rays. UVB causes sunburn at the outer layers of skin, but UVA causes sun damage that reach deeper layers of skin. Both UVA and UVB radiation can contribute to the development of skin cancer.
Padimate O is an organic compound related to PABA which used to be the most popular sunscreen, but most manufacturers stopped using it because it was thought to promote cancer rather than prevent it.
Padimate O is a yellowish water-insoluble oily liquid that absorbs UVB rays. There is some thought that it too may be carcinogenic because it causes indirect DNA damage. However, used in a food-grade concentration, Padimate O causes few allergic reactions.
Since more needs to be learned, it may be wise to limit use of sunscreens containing Padimate O for extended periods and to choose alternate sunscreens completely for children that exclude this ingredient.
Keep in mind that a sunscreen’s Sun Protection Factor (SPF) is a gauge of how well the formula protects the skin from UVB rays. It does gauge protection from UVA rays.