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Cinnamate compounds are widely used in sunscreens and cosmetics as UVB absorbers. An overview of cinnamate allergy, its causes, cross-reactions, diagnosis, and prevention.
A cinnamate is a compound closely linked to cinnamon oil and related compounds, frequently utilised as flavourings and fragrances in various toiletries and cosmetics. Due to their significant UVB absorption capabilities, cinnamates are used in sunscreen products and colour cosmetics that offer sun protection benefits.
The skincare industry predominantly employs octyl methoxycinnamate as its chief UVB-blocking agent. However, its effectiveness diminishes when exposed to sunlight, as it transforms into a form that absorbs UV light less efficiently. This degradation can be mitigated to some extent by incorporating certain photostabilizers such as bemotrizinol, enhancing the water resistance and stability of the product.
Octocrylene, a newer cinnamate variant, exhibits both UVB and some UVA absorption properties. It is recognised for its photostability and is generally considered non-allergenic and non-irritating. Nonetheless, its widespread application in sunscreens and cosmetic items has contributed to an increase in octocrylene sensitisation, positioning it as a leading photoallergen in chemical-absorbing sunscreens.
Cinnamate allergy manifests through its chemical similarity to balsam of Peru, tolu balsam, coca leaves, cinnamic aldehyde, and cinnamic oil, making individuals allergic to these substances potentially sensitive to cinnamates. The allergic reaction may take the form of classic allergic contact dermatitis or photocontact dermatitis, with symptoms emerging immediately or after a delay.
Concerns also surround the ease with which octyl methoxycinnamate penetrates the skin, possibly fostering the production of harmful free radicals. The long-term implications of cinnamate use in skincare remain uncertain, and further investigation has been called for.
Diagnosis of a cinnamate allergy involves conducting patch tests with 1% cinnamate in petrolatum. If a cinnamate allergy is confirmed, avoidance of products containing cinnamates is advisable. Treatment for cinnamate dermatitis may involve the use of topical corticosteroids and emollients, similar to the management of acute dermatitis or eczema.
To prevent cinnamate allergy, product labels should be read carefully and items containing cinnamates or their derivatives should be avoided. Those with a known allergy to balsam of Peru and similar compounds should particularly avoid sunscreens containing cinnamates. Consultation with a pharmacist for suitable alternatives is recommended.
Cinnamate is also known by the following names: 2-ethoxyethyl p-methoxy cinnamate, Cinoxate, Isobutyl salicyl cinnamate, Octyl methoxycinnamate, Octinoxate, and Octocrylene. The molecular formula for 2-ethoxyethyl p-methoxy cinnamate is C14H18O4, with a CAS number of 104-28-9.
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