Patch testing is a process to detect allergic contact dermatitis to something a person has contact with at home, leisure or at work. It involves applying patches with test substances in small chambers or discs to a person’s back. The patches are secured with hypoallergenic tapes. No needle pricking is involved. Patch testing does not test for urticarial (hives) or food allergy. A range of substances is used for this type of testing.
You will have three appointments made for you:
Monday - this is a 30 minute appointment with the nurse. The patches are applied to your back. Each strip contains a different substance to which you may be allergic. Additional tape may be applied to hold the strips in place. The patches are left in place for 48 hours and must be kept dry.
Wednesday - this is a 30 minute appointment with the nurse. The patches are removed, the skin is left to settle for 10 minutes to reduce redness and your back is checked to see if you have had a reaction to any of the substances.
Friday - This is a 15 minute appointment with the doctor. We check again, as there is the possibility that delayed reactions may have appeared since the patches were removed.
It is important that prior to having your patches applied:
- Stop taking your oral Prednisone for 1 week prior (Dr Becker will discuss this with you)
- You can keep taking oral Antihistamines
- Minimise use of any topical steroid creams and NONE has been applied to your back the day of testing - this is where the patches will be placed.
- Avoid sun exposure and tanning booths for 2 weeks before patch testing
In preparation:
- Wear comfortable clothing so that we can access your back easily.
- Ensure your back is clean and dry for testing - do not use moisturiser either please.
- Dr Becker may ask you to also bring specific suspect substances with you also to be tested at your first appointment.
- For men with a hairy back, shave the upper back two days prior to coming so that the patches adhere well.
Once the patches are applied, to give us the best opportunity to achieve a result, and to make sure the patches stay in place, please:
- Minimise sweating - no gym, jogging, lawn mowing etc
- Minimise upper body activity - no window washing, upper body exercises.
- PLEASE KEEP YOUR BACK DRY - you may sit in the bath, do not wash the patch test site. No showering for the entire time during testing - Monday to Friday.
- Do not apply creams or lotions to the patch test site.
- Avoid friction with clothing or chairs as this may loosen the patches.
- Do not expose the test area to the sun or ultraviolet light.
- Apply additional tape to any patch test strip that becomes loose, making sure that the test strip is affixed to the original area (you may need help to do this).
Positive Results
If patch testing reveals you are allergic to a substance or substances, the test is “Positive”. You will be given information about the substance that caused your skin to react.
Negative Results:
If your skin shows no reaction to patch testing, your results are “Negative”. Even if your results are negative, patch testing will help your doctor to manage your skin condition.
Side Effects and Risks:
Although patch testing can cause a reaction at the patch test site, the test has very few risks or side effects. You may experience itching at the patch test site after testing is completed, but this usually goes away within a few days.
