Shedding Light on Phototoxicity & Photoallergy Testing

As a formulator or brand manager, have you ever had complaints about your product despite having clean HRIPT results?  If so, you may want to consider what happens to your product when consumers go out in the sun.

Formulations contain a mixture of ingredients that have molecules that may be susceptible to alterations due to exposure to sunlight. This occurs when an ingredient or series of ingredients in your formula contain molecules that absorb natural sunlight (290-700 nm). The transformation of these photo unstable molecules can lead to a phenomenon known as photosensitivity, which can affect consumers of all skin types, and can be further classified into two distinct processes which can be tested clinically.

Phototoxicity (PT) is a skin injury that occurs in subjects with a single exposure to a sufficient dose of the photo-sensitive agent(s) and UVA radiation; it usually manifests as an exaggerated sunburn reaction confined to the light exposed area. Clinically, subjects have isolated duplicated test sites, both are treated with the test product and only one site is irradiated with UVA light. If any irritation score is observed over the treated and irradiated skin, the formulation demonstrates a phototoxic potential.

Photoallergy (PA) is an immunological response to a UV-modified chemical compound. Photoallergy includes an Induction and a Challenge phase. Clinically, duplicated test sites are treated with the test product and one site is irradiated with a calculated dose of UV light. Application of product and UV exposure are repeated multiple times (induction phase). After a rest period, subjects are challenged with duplicated treated sites, where one site is irradiated with a UVA dose, and post irradiation skin reactions are graded (challenge phase).  In PA, an inflammatory reaction, on the treated and irradiated site, can demonstrate a photoallergic potential for the test product.

Eurofins CRL currently performs both PT and PA studies on a routine basis and has dedicated experienced staff in this area of photobiology ready to conduct all your photosensitivity studies. Our lab runs these studies monthly for your convenience and we encourage you to reach out to your account manager for more details. As part of a good safety dossier, we recommend adding PT/PA data to your repertoire of testing for thoroughness and a piece of mind for your next personal care product launch.

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