Our patch testing facility is a specialist unit designed to find out if there is an allergic contact cause for your skin disease. In addition to patch testing, we can offer a full spectrum of blood allergy testing to see if there is an allergic component driving your skin disease.
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What is patch testing?
Patch testing tries to identify if there are any substances which are causing or aggravating your rash by coming into contact with your skin. Patch testing involves having sticky patches stuck to your back (or sometimes to other areas of non-affected skin like arms or legs). Underneath the patches, small compartments hold common household chemicals pressed tightly against your skin.
Examples of these include fragrances, colouring, preservatives found in creams, hair dye, metals, etc. These are all common chemicals found in everyday life and are not toxic.
A Patch Test can check for between 20 and 70 allergens at any one time. The testing requires three visits to the clinic over a five- or six-day period:
- The patches are applied and marked up with ink.
- 48 hours later the patches are removed, readings taken, and the areas further re-marked with ink.
- A further 48 to 72 hours later, final reading is undertaken.
Any fees charged for patch tests are inclusive of all visit and patch testing but will not include a follow-up visit with your consultant should this be necessary.
If any relevant allergens are identified that might be contributing to your skin condition, these will be discussed with you. Hopefully avoidance of these allergens will result in a great improvement in your rash. Sometimes patch tests can be negative and a contact allergy excluded.
Frequently asked questions
Keeping the patches dry is the most important aspect of accurate patch testing.
Water or moisture of any description will often cause the allergens to dissolve out of their chambers and often make results difficult to interpret.
For the whole 4 to 5-day testing period whilst the patch tests and ink markings are on your skin:
- Get the patches or markings wet in the bath or shower
- Work up a sweat by exercising too hard
- Go swimming
- Wear pale or valuable clothing as the ink may stain it
- Expose yourself to sunlight
- Take immunosuppressive medications (If you already taking these, patch testing is not likely possible as the results will be suppressed)
If the area becomes itchy, try not to scratch.
- Use the shower cautiously and attempt to sponge wash yourself whilst keeping the patches/markings out of the water flow
- Shower on the morning before your patch test (as you won’t be able to have a proper shower for at least a further 96 hours)
- Enjoy a holiday from exercise or sport that causes you to sweat
- If you notice a patch coming away, try to tape it down yourself
- Contact the clinic if you have questions or concerns
- Remember, these restrictions and recommendations need to cover the entire period from the first visit right through to the last, or the results may be invalidated
If you have a positive allergy, the biggest side-effect people suffer with will be itching. Sometimes you can also get an irritant reaction under the tape and this is also itchy.
- Occasionally reactions can become red, swollen or even blistered
- In strong positive allergies persistent reactions may occur which take a few weeks to disappear
- Eczema may flare up in the presence of positive patch test
- Inflammation can cause pigment change which may lighten or darken and sometimes lasts for a few months but is rarely permanent