Final Safety Assurance by Human Testing
Patch tests are conducted to evaluate the potential of an ingredient or product to cause irritation to human skin. The patch tests described here are different from those used by dermatologists to identify allergens in patients. The ingredient or product being tested is dispensed in set quantities into the chambers on a special adhesive bandage, which is then patched on the inside of the forearm of a subject for 24 hours. The next day, a person who is experienced in reading patch test results peels off the bandage and examines and scores the skin reactions such as redness or swelling under the patched area. (In some cases where appropriate, the patch test results are scored by a dermatologist.)
The stinging sensation is different from irritation associated with inflammatory symptoms such as rash or swelling. Stinging tests evaluate the potential of a cosmetic ingredient to cause uncomfortable sensory irritations such as itching, hot flush, tingling and pain.
First, panels of subjects who are sensitive to lactic acid or other compounds that cause sensory irritation are preselected. A certain amount of the product being tested is applied to the cheeks of subjects using a cotton swab. Each of the subjects on the panel records his/her symptoms and the degree of sensory irritation at predetermined time points. The results are evaluated after statistical processing with individual variability and application site differences taken into account.
To make sure a product causes no cutaneous or systemic problems, in-use tests are conducted using a preproduction prototype of the product under conditions of normal use.
The subjects are supplied with the prototype product along with instructions on application regimen and use the prototype product repeatedly for approximately 2 weeks or more. The subjects record their skin reactions on a survey sheet regularly throughout the duration of use. The survey sheets are collected and analyzed after the test is completed. In addition, in cases where appropriate, the reactions at the application site may be examined by a dermatologist or someone competent in reading such test reactions.
Repeated insult patch test
Repeated insult patch tests are conducted to evaluate allergenicity in human skin. A test substance such as ingredient or product is applied to the back of human subjects by using occlusive patches that remain for 24 hours per application for a total of 9 applications over a 3-week period. After a 2-week rest period, the subjects are challenged with another occlusive patch application again to see if any skin reactions occur to evaluate the allergenicity of the ingredient or product.
* Products that tested negative for allergenicity are labeled “DERMATOLOGIST-TESTED”.
Comedogenicity tests evaluate the formation of comedones, which are the cause of acne in human skin. A test substance such as ingredient or product is applied to the back of human subjects by using occlusive patches repeatedly for a total of 12 applications over a 4-week period. On week 5, samples of the stratum corneum are taken with stripping agent-coated slide glasses and examined microscopically to check for any comedones.
* Products that tested negative for comedones are labeled “NON-COMEDOGENIC.”
Patch test for sensitive skin
To make sure a product is compatible with sensitive skin, the product is tested by a patch test with occlusive patch application for 48 hours in volunteers with atopic dermatitis or contact dermatitis.
Skin reactions are examined by a dermatologist, with determination of the irritation index to make sure the product has a weak irritation potential.
* Products that demonstrated weak irritation potential or lower are labeled “TESTED ON SENSITIVE SKIN.”
Clinical safety evaluation of eye area products by ophthalmologist
This test is conducted to evaluate the ocular safety of skincare and makeup products used around the eye by ophthalmologist. Subjects use the actual product repeatedly for 2 weeks in accordance with the method of use prescribed for the product. Subjects also receive examinations and ophthalmology tests by an ophthalmologist before and after the test.
* For products that will be marketed in the United States only, those that tested negative in this test are labeled “OPHTHALMOLOGIST-TESTED.”
Human photo maximization test
Human photo maximization tests are conducted to evaluate the skin photoallergenicity of products. A test substance such as ingredient or product is applied to the back of human subjects by 24-hour occlusive patch followed by light exposure for a total of 6 cycles over a 2-week period. After a 2-week rest period, the subjects are challenged with another cycle of occlusive patch application and light irradiation again to see if any skin reactions occur to evaluate the photoallergenicity of the ingredient or product.