Metals especially nickel, fragrances, preservatives, adhesives and other substances can cause a contact allergy, which is a delayed type of reaction that builds up over 72 hours. This is not the same as an immediate type of reaction, such as certain types of food allergy, which are investigated with skin prick testing.
What does patch testing involve?
During your consultation, Dr Williams will review your history to identify any possible allergens you should be tested for. Before your patch test, you’ll be advised to protect the back from sun exposure and stop any topical steroids for at least two days before the test. You’ll also be advised not to apply body moisturisers on the day of the test.
Patches containing small quantities of a range of common allergens are placed into contact with the skin, typically on the upper back, which is kept in place for 48 hours. You need to keep the area of skin dry for the duration of the test, and avoiding strenuous exercise is therefore advisable. You must also not take any immunosuppressive medications while being tested as this can affect the results and avoid any sun exposure.
Patch testing involves three appointments. You will see the outpatient nurses on day 1 to apply the patches and day 3 to remove the patches and mark the skin again with pen and record any reactions. Dr Williams will see you on day 5 to assess for the presence and severity of any reactions and discuss their significance.
Are there any risks of patch testing?
If there are positive reactions there will be itching at the site, and severe reactions can cause localised blistering. You may experience a flare of your eczema triggered by the patch tests. In these situations treatment is prescribed to settle the symptoms. Occasionally there is a reaction at multiple sites which is known as the ‘angry back’ phenomenon.
Call 01483 555 907 to arrange a consultation with Dr Williams.