Table 4 Products

It has been well documented that in the investigation of patients suspected to suffer from contact dermatitis, the testing of their own (contact) products is necessary and highly valuable. Unfortunately, knowledge in this field is often minimal and profound mistakes are made. For example, concentrated biocides or plastic monomers are applied under occlusion in undiluted form causing bullous and ulcerative lesions and possibly active sensitization ('patch test sensitization'). On the other hand, products may be diluted too much or in an inappropriate vehicle resulting in false-negative reactions (8).

Tables 4.1 - 4.7 provide alphabetical listings of certain categories of products for which test recommendations have been recorded. As irritant reactions occur frequently, it is often advisable to test with several dilutions. When positive reactions are obtained, control tests should be performed, preferably on 20 controls or more. False-negative reactions also occur frequently, especially when a product has to be diluted for testing in order to avoid irritant reactions (e.g. soap, shampoo). Table 4.8 lists a number of products which should not be patch tested because of the (possible) risks involved, such as damage to the skin, systemic toxicity or patch test sensitization (8).

In the recommendations, it is often advised to test materials with the 'semi-open test' first. In this test, minute amounts of liquid products or products diluted with liquids are applied with a cotton swab on an area (1cm2) of the skin, allowed to dry completely and then covered with acrylate tape. The tape is removed after 2 days and read as ordinary patch tests (8,15).

For more information on testing patients' own products the reader is advised to read the relevant chapters in refs 8 and 15. Much of the information in this chapter has been derived from these sources.

The abbreviations used for the vehicles are as follows:

acet = acetone
alc = alcohol 70%
MEK = methyl ethyl ketone
oo = olive oil
pet = petrolatum

Table 4.1 SOLID MATERIALS

Solid materials, general (8,15)

Solid materials can be tested 'as is', placing scrapings or cut pieces in the test chamber, or they can be applied on acrylic tape, thus avoiding pressure effects (possibly leading to false-positive reactions). Depending on the material, the sensitizer can be extracted with water or solvents:

Paper alcohol
Plants and wood dusts alcohol, ether, acetone, aqua
Plastic materials acetone
Rubber materials acetone or aqua
Textiles alcohol

Solid materials, specific
Carbon paper as is (6), wetted with acetone (1,2)
Car steering wheel scrapings, as is (1)
Film, (un)developed as is (10)
Latex as is (6), after evaporation of irritant solvent (1)
Leather test with extracts (1,2)
Match as is (6)
Match box striking surface, as is (6)
Metal do not test (rough particles) (2)
Photographic paper as is (1,2)
Rubber objects as is and extracts (1,6)
Spectacles scrapings (6); solution of scrapings in acetone (1)
Vinyl films as is (6)

Table 4.2 COSMETICS AND TOILETRIES

Antiperspirant as is
Bath products, foaming 1% aqua (7); 0.1% aqua (8)
Bleaching creams as is (8)
Depilatories as is, open test (6); as is, semi-open test first (8); thioglycolate 1% pet (7)
Eye cream as is
Eyeliner as is (8)
Eye shadow as is (8)
Face cream as is
Face powder as is (8)
Foundation as is (8)