Patch testing is a procedure to find out whether your skin condition is a result of substances which have come into contact with your skin. This is known as a contact allergy. Substances that cause an allergic reaction can be from home, at work or in leisure activities. This type of allergy testing does not test for food allergies. Food allergies are tested through a blood test or prick test.

It is important to determine whether there is an allergic component contributing an eczematous reaction. Avoidance of relevant allergen(s) can be key in the management of the rash. It is possible that your patch tests will be negative, but this is helpful to your doctor as we can rule out contact allergy as a cause of your skin problem.

Patch testing involves four visits to the service. The first appointment is for an assessment and the three other visits all occur in the same week, usually but not always on a Monday, Wednesday and Friday. The initial visit is for an assessment where we will ask specific questions to individualise the test. Please bring your medication list to this appointment. At that visit, you will have the opportunity to book the dates of the test, which we will carry out on three days of the same week. On your first visit, we will apply each substance that needs testing to your back in special small discs (about 1cm in diameter) containers held in place by hypoallergenic tape. The substances will remain taped in place until your second visit, where we will then remove the taping and take note of any reactions. On the third visit, we will examine your back and we will discuss any reactions with you.

Positive reactions to a substance will include red and itchy skin around the substance area. These become more obvious by the third visit (final reading), although a reaction can occasionally take up to two weeks. Some substances may stain the skin; this is normal and will wash off after a couple of days with showering or bathing.