What is a Patch testing
Testing through a range of allergen series, patch testing can be helpful in identify substances that trigger skin conditions such as contact eczema and dermatitis.
What is involved in a Patch testing
For our patch testing we use the British Baseline series which reflect the most common and important causes of contact eczema and dermatitis. In total there are 41 allergens in the series which test for common allergens including chemicals found in fragrances, adhesives, rubber and metals such as cobalt and nickel.
Performed by either a Dermatologist or nurse, small quantities of substances are placed in contact with the surface of the skin by using Finn Chambers. These chambers are primarily placed on the Upper back and securely held in place with hypoallergenic adhesive tape for 48 hours before being removed. Three appointments are required. Usually a Monday, Wednesday and Friday with the patches being applied on the first appointment and the readings taking place on the second and third appointment. The first appointment takes around 30 to 45 minutes, depending on what has been requested for testing. The following appointments will take no more than 30 minutes.
Patients for patch testing require a referral from a Dermatologist. Referrals from GPs or allergy specialists are not suitable. If you do not have a referral for patch testing from a Dermatologist, we can book you in for a consultation with either Dr Martin Wade or Dr Anna Chapman at our clinic, for a consultation. They will prepare the referral for your patch testing.
The first appointment involves the nurse applying the patches, typically on your back. They will ask you to keep the area dry until they see you. Two days later, at your second appointment, the nurse will remove the patches and take the first 48-hour reading, recording all positive and negative reactions.
At the third appointment the nurse will take the final readings. You will then need a consultation with your referring Dermatologist, where they will interpret the results, discuss them with you and advise a treatment plan.
The Dermatologist will provide patient information leaflets on any allergens that patients may test positive for. These leaflets will help identify what daily items you come in contact with, that may contain the allergens you have reactive positive to. In some cases, the Dermatologist uses a patch test to rule out certain skin conditions, so they can diagnose appropriate treatment.
What is the cost of a Patch testing
You can find our fee schedule here.
What are the risks or potential side effects of Patch testing?
Sometimes an “Angry Back” can occur. This is when nearly all the test sites will become red and itchy leading to inconclusive and misleading results. This is most likely to occur when the patient has very active dermatitis or has multiple positive reactions and is referred to as a false positive result.
Patch testing may result in a flare of dermatitis, either in recurring areas of dermatitis or appearing in new areas for the first time.
Retesting can sometimes be required to clarify or confirm a reaction. This would be done as one allergen at a time.
When the patch test is positive occasionally the reaction may persist for several weeks and require treatment with a topical steroid.
Rarely, the skin may react to a new allergen as the result of the test, this would usually occur around 10 days after the test was applied.
In extreme cases a anaphylactic reaction may occur.
Is there any preparation needed before having Patch testing?
You will require a consultation with a dermatologist prior to the patch test who will review your medical history and look to identify potential allergens that you should be tested for.
You may be asked to bring some of your own products with you to your first appointment. Such as cosmetics, creams and ointments (including make-up, moisturiser, sunscreen), clothing (small sample up to 1cm in size required only) and identified food items. Only very small quantities are required of each item. If you work with industrial chemicals you may be asked to provide a data sheet for these, and to send some in one week prior to the appointment.
Please bring a list of your medications with you to your first appointment.
The back should be protected from sun exposure for 4 weeks before the tests. This includes sunbeds and phototherapy.
Creams and moisturisers should be avoided 4 hours prior to testing.
Topical steroids should be stopped at least two days before the test.
Wear old clothing to the appointments, as marker pen can stain.
What aftercare is required for Patch testing?
After the patch test is applied it is advised that you keep the back dry for the duration of the test. Therefore, no baths, showers, swimming or strenuous exercise which may cause unnecessary sweating should occur during this time.
Care should also be taken to avoid rubbing the patches off.
The back should not be exposed to the sun or sun beds during the test.
If the reaction to the patch test is extreme and causes blisters, some after care may be required such as washing and dressing the site of the blister.
Reactions to positive results may persist for several weeks and therefore may require topical steroids to ease the inflammation.
In most cases the skin will return to normal within a matter of days.