What are patch tests?
Patch tests are used in patients with dermatitis, to find out whether their skin condition may be caused or aggravated by a contact allergy. Patch tests are not the same as skin prick tests, which are used to diagnose hay fever allergy (house dust mite, grass pollens and cat dander). Skin prick tests have very limited value for patients with skin rashes.
There may be slight differences in methods used at other centres. For example, unlike the video, at our practice patients may shower or get their back wet after the patches are removed in 48h.
A range of substances can be used for patch testing. A baseline series together with specific tests appropriate to the individual may be applied. Each substance (known as an allergen) has been tested to find the best concentration to demonstrate an allergic reaction without causing irritation to those who are not allergic to the material.
Sometimes the results can be inconclusive. Further testing may be necessary. Patch tests do not always explain the cause of a dermatitis.