Dermatology - Contact Dermatitis Investigation Unit

Department of Dermatology
IMPORTANT

Please read this leaflet BEFORE you come for your first appointment

The Contact Dermatitis Investigation Unit is in the Barnes Building opposite the Mayo Building.

Contact dermatitis investigation requires detailed assessment before proceeding with the tests. Patch testing is used to identify or exclude allergic reactions on the skin due to contact (it does not identify any other sort of allergy e.g. food allergy). It will require four visits as outlined.

Assessment Visit (1st visit, usually Monday)

You will be seen by, or have a telephone consultation with, the doctor who will take an in-depth history of your problem. The information you provide will dictate what you will be tested with.

Remember to bring all materials outlined opposite. Note that the tests will NOT USUALLY be undertaken during the week of this visit. Please allow up to one hour for this visit.

2nd Visit (usually Monday)

A series of 50-200 tests will be put on your back (see photograph). Please allow up to one hour for this visit. Do not apply creams or ointments to your back before attending on that day.

3rd Visit (usually Wednesday)

The patches will be taken off and the doctor will look at your back. More patches may be applied.  Please allow up to one hour for this visit.

4th Visit (usually Friday)

The doctor will look at your back, then discuss the result of the test with you.  Please allow up to 2 hours for this visit.

Things to bring with you on your assessment visit

• A list of creams or ointments you have used
• Items to be tested e.g. creams and ointments, cosmetics, perfume, rubber gloves, shoes, materials handled at work etc. and their containers to see if these could be responsible for your skin problem.
• It is important to obtain the health and safety data for any chemical you bring from work

Any products left with us after completion of your patch tests will be disposed of. Please ensure you collect these at your final visit.

During the test please follow the following instructions

• Do not wash your back during the test period even when the patches have been removed
• Wear an old top next to your back so that it does not matter if it becomes stained
• Avoid any sports or exercise
• Avoid rubbing or scratching your back during the test
• Do not expose your back to sunlight during the test
• Secure any patches which become loose with nonallergic tape

Please note the following:

• You should not expose your back for sunbathing or use a sunbed for 2 weeks before your test
• We cannot patch test if you are pregnant and/or breastfeeding 
• Any exccess hair will need to be removed prior to applying patches
• If you have any further reactions on your back within 3 weeks of the tests being completed, please contact the unit

Frequently asked questions

1.    What are the benefits?

When a relevant contact allergy is identified, advice can be given to reduce or even eradicate your skin problem and reduce or eliminate the risk of future recurrences.  It may guide your doctor with regard to safe treatments for you.

2.    If my tests are negative has it all been a waste of time?

We don’t think so because the negative finding helps your doctor focus on alternative explanations for your condition and excludes concerns about the possibility of contact allergy.

3.    Why have I been tested for substances which don’t seem to apply to me?

Experience has shown that patients [and doctors] are poor at predicting their contact allergies. By doing this, we commonly find unsuspected allergies relevant to the cause of the skin problem. As new allergens are identified we need to screen patients for allergy to them to establish their importance.

4.    What side effects may occur?

Patch testing is a routine investigation which has been carried out for over 100 years. It is a non-invasive test with an excellent safety record. Short-lived minor discomfort and irritation from positive patch tests and under the adhesive of the test units is quite common and will not be expected to cause any significant difficulty.

The following effects are very uncommon but have been reported:

1. Very strong positive reactions to test substances may result in a small blistered area on the back [rare]
2. Multiple strong reactions may result in several itchy blistered areas on the back [exceedingly rare].
3. A more generalised flare of eczema may occur either over the back or at the site of the original skin problem [exceedingly rare].

The previous three risks noted would be expected to be short- lived and last no longer than one week and settle with treatment if this is necessary.

1. Allergy: there is a tiny chance you may become allergic to one of the substances applied during patch testing. In practice this does not seem to cause a problem in the long term [exceedingly rare]. 
2. In patients with dark skin there is a chance of causing hyperpigmentation [increased darkening of the skin] or depigmentation [lightening of the skin] at the site of the patch test but this would not be expected to be permanent [exceedingly rare].
3. Scarring and infection are possible at the site of patch testing [exceedingly rare].

If you have any concerns or questions about your patch tests, please ask any of the staff who will be pleased to answer your questions

If you have any queries about your test, contact:

Nurse in Charge - 0161 206 1038
Sue Parkinson - Consultant Secretary - 0161 206 1014

Number to contact to change new patient first attendance assessment visit
Change Patch Test Assessments Only: 0161 206 7482

Number to contact to change patch assessment 2nd/3rd/4th visits
Change Patch Test Application Appointments: 0161 206 1007