Chemical UVB sunscreen/sunblock: octyl methoxycinnamate (octinoxate)

Generic name: octyl methoxycinnamate; octinoxate

Brand(s): various

Type: Chemical

Range of UV spectrum covered: UVB

Wavelengths covered: 280-320 nm

Stability:
When exposed to sunlight octyl methoxycinnamate is converted into a less UV absorbent form (from E-octyl-p-methoxycinnamate into a Z-octyl-p-methoxycinnamate). This conversion can be partly prevented by certain other UV blockers, particularly bemotrizinol (Tinosorb M).

Summary:
Octyl methoxycinnamate (octinoxate) is a chemical sun blocking agent that absorbs ultraviolet radiation in UVB range. When exposed to sunlight octyl methoxycinnamate is converted into a less UV absorbent form, which reduces is effectiveness. This conversion can be partly prevented by certain other UV blockers, particularly bemotrizinol (Tinosorb M). Safety concerns have been raised regarding possible estrogenic and other adverse effects of octyl methoxycinnamate, especially in children and pregnant women. More research of this issue is needed. Octyl methoxycinnamate is absorbed into the skin and has been shown in some studies to promote generation of potentially harmful free radicals. The health implications are unclear but some experts have raised concerns that warrant further research.

Details:
Octyl methoxycinnamate is an oil soluble chemical sunscreen agent that absorbs UVB radiation. It does not protect against UVA. It is the most widely used UVB blocking agent in the skin care industry.

When exposed to sunlight octyl methoxycinnamate is converted into a less UV absorbent form (from E-octyl-p-methoxycinnamate into a Z-octyl-p-methoxycinnamate), which reduces its effectiveness over time. This conversion can be partly prevented by certain other UV blockers, particularly bemotrizinol (Tinosorb M). The safety implications of such conversion are unclear.

Animal studies indicate that octyl methoxycinnamate may produce hormonal (estrogen-like) and possibly other adverse effects. Whether typical human use of octyl methoxycinnamate may cause such effects is unclear. Children and pregnant women tend to be particularly vulnerable to hormonal effects and their use of octyl methoxycinnamate is of particular concern. More research of this issue is needed.

Octyl methoxycinnamate is relatively easily absorbed into the skin and has been shown in some studies to promote generation of potentially harmful free radicals. Implications of these finding for typical use are unknown but some experts have raised concerns that warrant further research. (See our article on possible risks of absorbable chemical sunscreens.)