Patch Testing
Patch testing is used by dermatologists to identify substances that may trigger allergic contact dermatitis on the skin.
At The London Skin and Hair Clinic, patch testing is performed by dermatologists to investigate ongoing rashes or eczema that may be caused by allergic reactions to everyday substances.
Minute quantities of diluted allergens are placed on the skin using a series of patches, which are covered by tape. The reactions are then assessed during follow-up appointments over several days.
Highly effective way of identifying and confirming what is causing allergic contact dermatitis
Series of panels of allergens are applied to the skin on a Monday, and readings taken on Wednesday and Friday
A referral from a Dermatologist is required in order to have patch testing
We use the British Standard Series for patch testing
What is Patch Testing?
Patch testing is used by dermatologists to identify substances that trigger allergic contact dermatitis.
By testing the skin’s reaction to small amounts of common allergens, dermatologists can determine whether everyday products or materials are contributing to ongoing eczema, dermatitis or unexplained skin irritation.
At a Glance
- Guide Price: £500 for British standard series, additional charges for additional series.
- Frequency: Three appointments on a Monday, Wednesday, Friday, each around 30 minutes.
- Risk: Active sensitization, rash and dermatitis, rarely anaphylaxis.
- Aftercare: Avoid showering and getting the patches wet until the final reading of the patches on the Friday.
What is involved in 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 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 on Monday, Wednesday and Friday, with the patches applied during the first appointment and the readings taking place during the second and third appointments.
The first appointment takes around 30 to 45 minutes, depending on what has been requested for testing. The following appointments usually take no more than 30 minutes.
The first and second appointment are usually performed by the nurse who will apply the patches and take the first 48-hour reading, recording all positive and negative reactions.
The third appointment is conducted with a dermatologist who reviews the final results and explains any positive reactions.
Patients attending for patch testing at our dermatology clinic in London will also receive guidance on which everyday products may contain the allergens identified during testing.
In some cases the dermatologist may use patch testing to rule out allergic contact dermatitis when diagnosing other skin conditions.
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.
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.
Follow-up appointments allow the dermatologist to review the results and discuss strategies for avoiding substances that trigger skin reactions.
What is the cost of Patch Testing?
You can find our fee schedule here.
The cost of patch testing will depend on the consultation and the allergen series recommended by the dermatologist.
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.