Skin Tolerance Tests

Skin Sensitisation

Sensitisation (allergy) is an uncommon skin reaction to specific components of topical products. However it’s severity and persistence means that when it occurs it is serious problem for the subject concerned. These tests investigate the potential of products to cause sensitisation. All tests have an induction period of 2 to 3 weeks during which exposure to potential allergens occurs followed by a challenge at a distant body site. A positive result on challenge is indicative of systemic sensitisation; i.e. the subject has become allergic to the product.

Sensitisation patch test

• A minimum of 100 subjects are needed for reliable information
• Two weeks induction period with continuous exposure under occlusion to the product
• Induction on the skin of the back
• Challenge in fourth week at a distant site, e.g. the upper arm

Sensitisation patch test (variation for USA)

• A minimum of 200 subjects
• Three weeks induction period with continuous exposure to the product
• Induction on the skin of the back
• Challenge in sixth week at a distant site, e.g. the upper arm

Photo-sensitisation (photo-allergy) test

Some chemicals only become allergens after exposure to UV or rarely, visible light. This assay was developed by Kaidbey and Kligman and is designed to detect photo-sensitisers using a procedure similar to the sensitisation patch test.

• Normally 25 subjects
• Three weeks induction period with intermittent exposure to the product followed by UVB irradiation
• Induction on the skin of the back
• Challenge in sixth week at a distant site
• Challenge consists of 24 hour exposure followed by irradiation with UVA