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patch test information leaflet

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What is patch testing?


  • Patch testing can help your doctor find out if your skin condition is due to an allergy caused by something that is regularly in contact with your skin.
  • Skin contact with an allergen might occur at home, at work or during your free time.
  • Patch Testing does not test for food allergies, animals, dust or pollens.
  • Patch testing is not painful and does not involve any injections.

This test is done in our Dermatology Department, the address and directions are at the end of the page.


What must I do before my first Patch Test appointment?


  • You will be tested to around 40 standard substances commonly in contact with the skin, including nickel, preservatives, perfumes and rubber.
  • Additional substances will be included depending on your skin problem.
  • You may be tested to some of your own work or home products.

When would we NOT patch test you?


One week prior to patch testing please contact the department if:

  • You are taking steroid tablets (over 10mg per day) Prednisolone.
  • You have extensive eczema on your back.
  • You are pregnant / breastfeeding.
  • If you have had sun exposure including sunbeds or light therapy in the past two weeks.

Can I take anti-histamines during patch tests?


Yes, you can continue to take anti-histamines, but please inform us at your first patch test clinic appointment.


What to bring on your first appointment


  • Your own products, substances that you have you have been advised by the doctor that you might be allergic to.
  • Work chemicals, if the doctor thinks that chemicals at work may be causing the problem, please deliver samples in well-sealed and labelled containers 2 weeks before your appointment to the dermatology unit.

Please bring the Health and Safety Data sheets, which will be available in your place of work. The doctor will advise you if this is required.


What does patch testing involve?


You will need to attend the hospital on 3 separate days in the week.

On the first visit:

you will be assessed by the nurse.

  • The substances to be tested will be applied in special small containers to your back attached by hypoallergenic tape.
  • Please do not apply a moisturiser to your back on the morning of this appointment.
  • The sites are marked with a skin marker pen. If you have a very hairy back it would be helpful if you could shave the area before attending your appointment.

On the second visit, 48 hours later, most of the patch tape is removed and any reactions noted. Only the top of the tape and marker pen will remain.

On the third visit, 96 hours later, your back will be examined and any reactions discussed with you by the doctor.

  • The sites may itch. This is normal.
  • Positive reactions become red and itchy at the test site and usually become apparent by the third reading.

What happens if all the patch tests are negative?


This is helpful since, as far as we can, we have eliminated contact allergy as a cause of your skin problem.


How should I care for my patch tests?


  • Please keep your back dry during the whole week (until after your 3rd visit) of the tests.
  • Do wear dark clothing and not your best clothes as the marker ink may stain.
  • Do not expose your back to the sun during this procedure.
  • Do avoid sport or heavy physical work during the tests.
  • Sweating can lead to the patches peeling off.
  • Do wear old clothing and a T-shirt or vest at bed time in order to help keep the patches in place when sleeping.
  • If a patch starts to peel off, reinforce with medical tape.
  • If the whole patch test comes of, please do not reapply it. Make a note of the date and time the tape came off and inform the doctor or nurse at your next patch test appointment.

What side effects may occur?


Side effects include:

  • Skin reddening and itching. This is usually a small patch of skin and disappears after a few days.
  • Staining of the skin under the patch test tape will usually disappear after a few days.
  • Skin pigment change. An increase or decrease in pigment may sometimes be seen at the site of the patch tests.
  • A flare of eczema may occur although this side effect is rare.

Sources of information and advice


If you would like to find out more about patch testing you may find the following websites helpful:

British Association of Dermatologists

DermNet 

If you have any concerns about your appointment or treatment, please call the telephone number below:

Brighton General Hospital Patient Helpline: 01273 665140

Disclaimer: the information in this leaflet is for guidance purposes only and is in no way intended to replace professional clinical advice by a qualified practitioner.


Publication Date: January 2019

Review Date: November 2021

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