Skin allergies

Your appointment

We offer face-to-face appointments.

We cannot carry out patch testing if you're pregnant.

How to get an appointment

You can ask your dermatology specialist to refer you.

Changing or cancelling your appointment

Phone: 020 7188 6272  

Email: [email protected]

Please give us as much notice as possible if you cannot come to your appointment so we can offer it to someone else. 

If you do not contact us to cancel your appointment, we'll cancel your 2 follow-up appointments. We'll write to your doctor and ask them to refer you again if necessary.

Before your appointment

We'll write to you before your appointment with information about patch testing. Please read this before you come to the hospital.

Please bring with you:

  • any products you think might aggravate your skin
  • any products you use regularly such as toiletries, cosmetics and medical lotions or creams. We'll need to take a small amount of them to do the test. If you cannot bring samples, please bring a list
  • an old shirt, vest, blouse or T-shirt to wear during patch testing. This is because a small amount of test substances, skin marking ink and petrolatum (used to dilute the allergens), may stain

Do not apply any creams or moisturisers to your back for a day before the tests.

If your back is very hairy, please shave or clip the hairs away at least a week before your first appointment.

Please contact us before your appointment if you're on:

  • prednisolone tablets (more than 15mg each day), or
  • medicines that suppress your immune system, such as methotrexate, azathioprine or ciclosporin

We may need to delay your tests.

Ultraviolet (UV) light (from sunlight) can suppress a patch test reaction. Because of this, we do not patch test on tanned skin and recommend no UV light exposure from the sun or sunbeds for 6 weeks before the test.

During your appointment

When you arrive, please check in at the reception desk or using the self-service kiosk. 

Please let our receptionist know if any of your contact details have changed.

Your appointment can take up to 2 hours as you may see different members of our team, including specialist doctors and nurses.

We're a teaching hospital and postgraduate dermatology students may be present. Please let us know if you do not want them at your appointment. This will not affect your care.

Most people need 3 visits.

Your patch test

At the first appointment your doctor will ask about your history and decide which substances to test for. Small chambers containing the substances we want to test are taped in place on your back by an experienced nurse.

We'll ask if we can take a photograph of your back with your own phone (if you have one) to record the test application site.

The test chambers are removed 2 days after application. This might be done by you or at our clinic. The marking tape with the numbers should be left in place until your final reading. You'll be given instructions on how to do this.

The second appointment is on day 2 or 3 after the chambers have been applied. The first reading of any reactions is made in our clinic. If there is a doubtful reaction, a test might need to be repeated.

The third appointment is on day 7 after the chambers have been applied. The second reading of any reactions is made. This will help confirm if the first readings are true allergic reactions (still present) or identify new reactions (not seen at day 2 or 3). Sometimes a third reading is necessary, but we'll let you know during your last appointment.

Discomfort from patch testing is usually minimal.

During your last appointment your doctor will explain the results with you.

After your appointment

After your last consultation, you can bathe or shower normally. Any staining of the skin will go within a few days. Any positive reactions will normally settle over a few days but can be longer. A steroid cream can be used to speed this up.

Do not:

  • get your back wet during the week you are tested. You can sit in the bath and shower your front but your back must be kept dry
  • take part in activities that might dislodge the tests by excessive sweating or stretching


  • contact us with any problems
  • remove the tests if they cause unbearable itching or discomfort
  • apply extra tape if the tests are coming loose
  • wear night clothes to protect the tests

After your tests we'll write to the doctor who referred you and send a copy of the letter to you and your GP. If you need any follow-up appointments, these will be made with the referring doctor.

If you have any questions or concerns, please contact us using the details you are given at your first appointment.

Last updated: January 2024

Contact us

For more information, please contact us.

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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