Allergy Testing involves patch testing for allergic contact dermatitis and irritant contact dermatitis.
Allergic contact dermatitis and irritant dermatitis is common. It is often mis-diagnosed as eczema and as a result can cause long term suffering by the patient due to lack of avoidance of contact with the offending allergens. Potential allergens are extensive and are found in cosmetic products, shampoos, conditioners, clothing, contact with rubber, metals and other chemicals and environmental/occupational exposures. Occupational exposure is common in the hairdressing industry, building industry and food industry. It is imperative to identify the offending allergen/s and it’s related/cross reacting chemicals in order to successfully avoid contact with it and control the allergic dermatitis.
Dermatologists perform skin tests called Patch Testing to help identify the allergen/s (substance that causes allergy) and help treat the allergy. These tests are usually performed by application of a tiny amount of allergen onto the skin. The patches are made specifically for the individual person and are usually applied to the back on a Monday and removed on a Wednesday to allow the first reading. The final reading is usually done on a Friday to identify the delayed type hypersensitivity reactions resulting from contact with the allergens. During this 5 day period, it is a requirement that the back is kept dry and no activity that causes sweating is undertaken. The dermatologist will then be able to discuss the results with the patient and provide written information with the names of other cross reacting chemicals that should be avoided.
The advantages of patch testing include-
• Identify the cause of the allergy
• Identify the numerous names that one chemical may be known by on labels.
• Identify other cross reacting chemicals that should also be avoided.
• You can go to work wearing the patch.
• Once the allergen/s have been indentified and avoided, the “dermatitis” is cured, usually only recurring if exposure to the allergen occurs.
The patch test has no major disadvantages except the inability to wash your back for 4 days.