Skin Tolerance Tests

Irritancy Tests

3-day patch test (Two consecutive 24 hour applications)

Screening test for previously tested products that have had minor changes in formulation. Also suitable for products that are only applied to the skin occasionally or for only short periods of time.

• Normally 25 subjects
• Test for up to ten products at a time
• Suitable for both rinse-off and leave on products

96 hour patch test (Four consecutive 24 hour applications)

Suitable for previously tested products that have had a significant change in formulation and are leave on products or are applied to the skin frequently.

• Normally 25 subjects
• Test for up to ten products at a time
• Suitable for leave on products
• Gives indication of potential skin irritancy due to chronic exposure

14-day patch test (HRIPT)

Maximum reassurance of product safety. Suitable for newly formulated previously untested products where no previous product experience exists. Especially suitable for leave on products that are frequently applied to the skin especially to sensitive areas such as the face, e.g. facial moisturisers.

• Normally 25 subjects
• Test for up to ten products at a time
• Suitable for leave on products
• Gives indication of potential skin irritancy due to chronic exposure

Soap Chamber Test

Test developed by Frosch & Kligman for surfactant containing products (soaps, detergents, shampoos, etc). Intermittent applications over a seven-day period designed to emphasise differences between products. It is a comparative test and is useful for benchmarking new products with existing ones. Can be used to support the claim of mildness.

• Normally 20 subjects
• Test for up to six products at a time
• Key features of surfactant damage scored, erythema, scaling (dryness) and fissuring (cracking)
• Statistical analysis possible using within subject comparison procedures

Photo-Irritancy Test

Some chemicals only become skin irritants after activation by UV or visible light. This test was devised by Kaidbey and Kligman to screen topical products for photo-irritancy.

• Normally 12 or 20 subjects
• Six hour exposure under occlusion
• Two or three products test at one time
• Statistical analysis possible using within subject