Photoallergy test

Photoallergy testing is an essential clinical assessment to determine whether a substance causes an allergic reaction after exposure to (UV) light .
This analysis is carried out on human volunteers under medical supervision and according to strict ethical protocols. It aims to identify photosensitizing compounds that may induce skin reactions when exposed to sunlight.

Photoallergy testing is a key tool in validating the safety of cosmetic and sunscreen products , particularly those containing plant extracts, perfumes, UV filters or colorants .

Principle and test protocol

The study is based on the application of a test substance to the skin , followed by controlled exposure to UV-A or UV-B radiation .
The skin is then observed to assess local reactions (erythema, edema, pruritus).

The protocol generally includes:

1. Induction phase : repeated application of the product to a given skin area.
2. Irradiation phase : exposure to a calibrated light source.
3. Observation phase : delayed reading of skin reactions to distinguish photoallergy from simple phototoxicity.

Unlike the phototoxicity test , photoallergy involves a delayed immunological mechanism , requiring prior sensitization.

To complete this assessment, YesWeLab also offers:

• the phototoxicity test ,
• assessment of skin tolerance ,
• and the study of light stability for photosensitive formulas.

Industrial applications

The photoallergy test is particularly recommended for:

• Cosmetic and sun care products : validation of the safety of UV filters, perfumes, colorants, essential oils or botanical extracts.
• Plant active ingredients : identification of potentially photosensitizing molecules (coumarins, furocoumarins, bergapten, psoralen, etc.).
• Topical pharmaceutical products : control of photoinduced reactions linked to excipients or active ingredients.
• Food supplements : safety of photosensitive extracts intended for sun exposure.

The objective is to ensure the safety of use of products exposed to light , while respecting European regulatory requirements (EC Regulation No. 1223/2009).

Analytical interest and complementarity

Photoallergy tests are part of a set of safety and skin compatibility analyses used to assess the behavior of formulations under light exposure.
They are often associated with:

• the photostability study to check the degradation of the ingredients,
• the OECD 429 skin sensitization test ,
• the in vitro cytotoxicity test ,
• and the evaluation of thermal stability to characterize the overall behavior of the product.
• These combined tests ensure a complete characterization of the safety profile of formulations, from development to marketing.

YesWeLab Services

YesWeLab works with a network of ISO 17025 and/or COFRAC accredited partner laboratories , specialized in toxicology, photobiology and cosmetic clinical trials .
Our experts select the protocol best suited to your matrix, whether it is a raw ingredient, a cosmetic prototype or a finished product .

Thanks to the YesWeLab digital platform , you can submit your analysis requests online, track your samples and access your reports with complete transparency.
Since 2020, YesWeLab has been supporting cosmetic laboratories, sun care brands and formulators in validating the tolerance and photo-induced safety of their products.

For any specific requests or quotes, contact our scientific team today.