Octyl methoxycinnamate is a chemical ingredient found in some brands of sunscreen and lip balm that blocks UV-B rays from the sun to protect the skin against harmful radiation. It is considered the most commonly used chemical for blocking UV-B rays. Controversy exists over whether or not octyl methoxycinnamate may harm humans who use products with the chemical in them. The chemical is termed octyl methoxycinnamate by the International Nomenclature of Cosmetic Ingredients (INCI), which provides names for certain chemicals and other ingredients used in soaps, cosmetics and related ingredients. It is referred to as octinoxate according to the United States Adopted Names (USAN), which provides individual names for pharmaceutical products sold in the United States.
The chemical is an organic compound formed from methoxycinnamic acid and 2-ethylhexanol. When mixed together, they form a clear liquid that does not dissolve in water. It can absorb UV-B rays from the sun but does not protect against UV-A rays. Both types of rays are dangerous to humans, and other ingredients may be included in sunblocks and lip balms to offer full protection.
Sunblock functions by absorbing certain wavelengths of light. The chemicals and ingredients in sunblocks are designed to absorb light at the specific wavelengths the sun emits. The thickness of the sunblock itself also forms a physical barrier to protect the skin as well as the chemical barrier provided from the ingredients. Different varieties of sunblock provide differing levels of protection. Thinner sunblocks may feel more comfortable to apply but may not protect the user as well as the stronger, typically thicker sunblocks.
Safety concerns over octyl methoxycinnamate arise from the possibility that the chemical may break down and absorb into the user's skin when it comes into contact with sunlight. Chemical reactions that occur then happen underneath the protective barrier a person's skin provides and may be absorbed into the body. This may lead to temporary problems such as skin irritation or long-term problems such as increasing the user's risk of developing cancer and causing the skin to age more quickly.
Though tests have been performed, no conclusive evidence has been found and it is uncertain what the exact effects of octyl methoxycinnamate are. More research is needed to determine whether or not the chemical poses a risk when used in products applied to the skin. Until then, users can try other methods to protect themselves against the sun and check the ingredients in the sunscreens and lip balms they use.