Patch testing is a specialised investigation used to identify whether a skin rash is caused by an allergic reaction to substances that come into contact with the skin, such as fragrances, preservatives, metals, or adhesives. It is particularly helpful if you have eczema that is new, behaving differently from your usual eczema, or proving difficult to manage.
How does it work?
During the test, small amounts of common allergens are applied to the back using adhesive patches. These are left in place for 48 hours, after which the patches are removed and the skin is checked. A final reading is usually taken a few days later to confirm whether any delayed allergic reactions have developed. Patch testing helps pinpoint potential triggers so they can be avoided in the future, leading to clearer skin and fewer flare-ups.
FAQ’S
Frequently Asked Questions
What should I bring to my appointment?
Your doctor will arrange a series of patch tests tailored to your allergy history and risk profile. You are encouraged to bring along any personal products that may be related to your rash, as your doctor can assess whether these should also be included in the testing.
How long does the process take?
You will need 3 clinic visits over the course of a week (typically Monday, Wednesday, and Friday)—one to apply the patches, another to remove them, and a final reading a few days later.
Do I need to avoid anything while wearing the patches?
Yes. The patches must stay dry and in place, so you should avoid showering, swimming, or strenuous exercise that causes heavy sweating until they are removed.
Can patch testing be done during pregnancy?
No. Patch testing is not recommended during pregnancy, as the results can be less reliable and there are safety considerations. Your dermatologist will advise on the best timing if you are expecting or breastfeeding.
Is patch testing the same as skin prick testing?
No. It’s important to note that patch testing is different from skin prick testing, which is performed by allergists to investigate hay fever, asthma, or food allergies. Patch testing looks for delayed skin reactions to substances that touch the skin, rather than immediate reactions.
What happens after testing?
Your dermatologist will discuss the results with you, explain what the allergens mean, and provide advice on how best to avoid them in your daily life.