Patch Testing
Often, patients will have rashes or hives that appear for no apparent reason. Skin testing may produce a negative result to common allergens. If this is the case, the doctor may use a patch test.
Patch testing is a simple procedure to help diagnose allergic contact dermatitis and identify the causative agent(s). Often these agents are chemicals found in common household products such as cosmetics, cleaning products and even jewelry.
Two patches are placed on your skin and held in place with tape. They stay on your skin for 48-72 hours, after which you return to the office for the doctor to read the results. While the tests are on, it's important to not get the tests wet, either by showering or by participating in vigorous activities that may cause you to sweat. You may find the tests get itchy or burn, but it's important not to scratch them. Should they become loose, use hypoallergenic tape to replace them, taping only the edges of the test strip.
If you react to one or more of the substances, the doctor will let you know what products likely contain that substance so you can avoid them.