Allergy Testing
Patch testing is used by dermatologists to determine whether your skin condition is caused by an allergy to substances that come into direct contact with the skin (allergic contact dermatitis).
Patch testing does not detect allergies related to diet or inhaled substances that may cause symptoms such as sneezing, asthma, or hives. These reactions are investigated using skin prick testing or blood tests for specific IgE antibodies.
Patch testing requires two - three appointments over one week, and it is important that you attend all appointments on the specified days.
Patch testing is only carried out following referral from another dermatologist or after an assessment within the clinic, where allergic contact dermatitis is suspected.
Initial Consultation
Your dermatologist will review your medical history and determine which substances (allergens) should be included in your test. A pre-test diagnosis will also be discussed during this consultation.
Day 1 – Saturday: Application of Patch Tests
During the test, you will be exposed to approximately 50–70 standard substances that commonly come into contact with the skin. These may include:
- Rubber
- Chemicals
- Metals
- Perfumes
- Plants
Additional substances relevant to your particular condition may also be included. In some cases, we may test products from your workplace or home.
Small chambers (patches) containing the allergens are applied to your back using adhesive tape. This will be done by the patch test nurse, who will explain the procedure and answer any questions you may have.
The back is usually used as it provides a convenient testing area. Occasionally, patches may be applied to the upper arms or other areas if there is active eczema on the back or if there is insufficient space on the upper back for all test chambers.
With your consent, a photograph of the test area will be taken using your own phone to record the position of the patches.
Day 3 – Monday: Removal of Patches
The patches remain in place for 48 hours before being removed.
You will remove the patches yourself at home. After removing them, please ask a family member or friend to take a photograph of the test area using your phone.
You will be provided with a pen to remark the patch sites after removal.
Day 5 – Wednesday: Reading of Results
You will return to the clinic for the patch test reading with Dr Hodder.
The test sites will be examined, and your photographs from the previous day will also be reviewed to determine whether any reactions have occurred.
If a reaction is uncertain or doubtful, a test may need to be repeated.
Dr Hodder will discuss the results with you and explain the final diagnosis and its implications.
After the Test
Following the tests, you may bathe or shower normally.
Any temporary staining of the skin will fade within a few days. Positive reactions usually settle within a few days, although occasionally they may last longer. A topical steroid cream may be prescribed to help the reaction resolve more quickly if needed.
Test Report
A written report summarising the tests performed, results, and interpretation will be sent to the referring dermatologist, with a copy provided to you.
