4-Methylbenzylidene camphor

4-Methylbenzylidene camphor, short 4-MBC, also 3-(4-Methylbenzylidene)bornan-2-one, or 3-(4-Methylbenzylidene)-dl-camphor is an organic camphor derivative that is used in the cosmetic industry for its ability to protect the skin against UV, specifically UV B radiation. As such it is used in sunscreen lotions and deodorants. Its tradenames include Eusolex 6300 (Merck) and Parsol 5000 (Givaudan).

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Mechanism

All the camphor sunscreens are supposed to dissipate the photon energy by trans-cis isomerisation. But for Parsol 5000 the quantum yield for this isomerisation is reported to be only between 0.13 - 0.3. This low quantum yield means that other photochemical processes are occurring.^[1]

Endocrine disruptor

Studies have raised the issue that 4-MBC acts an endocrine disruptor. There is controversy about the estrogenic effects of 4-MBC and while one study showed only a relatively minor effect^[2], a study in Switzerland showed significant uterine growth in immature rodents.^[3] In addition, there is some evidence that 4-MBC may suppress the pituitary-thyroid axis leading to hypothyroidism.^[4]

The agent can also lead to a photoallergic dermatitis.

Approval status

4-MBC is approved for use in Europe by the European Union's Scientific Committee for Cosmetic Products & Non-Food Products but is not approved for use in the USA by the Food and Drug Administration. It is also approved in Canada by Health Canada, in Australia and other countries. It's not permitted in Japan.

Alternative agents

Alternative agents that block UV by absorption include:

• Avobenzone
• Oxybenzone
• octyl methoxycinnamate (OMC)
• homosalate

See also

Xenoestrogen

References

1. ^ Sun Protection in Man. Chapter 26: Cantrell, Ann; McGarvey, David J.; Truscott, T. George. Photochemical and photophysical properties of sunscreens.
2. ^ [1] Low estrogenic activity
3. ^ [2] Significant estrogenic activity
4. ^ [3] Inhibition of pit-thyroid axis