Skin patch testing

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Contact dermatitis is a common condition that causes an itchy skin rash when your skin comes into contact with a particular substance. It is a type of eczema (the name for a group of conditions that cause skin irritation and dryness), but unlike the most common type of eczema (atopic dermatitis), it isn't linked to other allergic conditions such as asthma and hay fever and doesn’t run in families.

Contact dermatitis can occur on any part of your body but is most common on the hands and face. Symptoms normally occur within a few hours of exposure to the allergen or irritant.

Contact dermatitis usually gets better when you avoid contact with the substance that triggers it.

Symptoms of contact dermatitis include:

• An itchy rash
• Patches of skin that are darker than usual (hyperpigmentation) - this is more common on brown or black skin
• Dry, cracked, scaly skin
• Blisters and bumps that may ooze and crust over
• Swelling, burning or tenderness
• Black or brown skin may become dark brown, purple, or grey
• White skin typically becomes red

Your consultant will ask you about your symptoms, general health, and medical history. They will also ask you questions about your work and home environment to help identify which substances to test.

Your consultant will examine your skin for signs of contact dermatitis such as redness and a rash. 

If your consultant thinks skin patch testing is an appropriate procedure for you, they will give you an appointment with a nurse who will perform the procedure. 

Skin patch testing may not be suitable for you if you:

• are pregnant
• are breastfeeding
• have extensive eczema or another skin condition on your back
• have sunbathed or used a sunbed in the previous six weeks
• are taking prescribed steroid tablets

How is a diagnosis made?

Your consultant will make a diagnosis based on your symptoms and the results of your skin patch tests.

Why is this first consultation so important?

At Circle Health Group, your first appointment is important as it's where you will first meet your consultant, the doctor responsible for your care. Your first consultation is also where we get to know you, discuss your symptoms and how they impact your life, and your expectations for treatment. It is important to us that you are as well-informed and comfortable as possible during your time with us, so please take the opportunity to ask your consultant any questions you may have at your first appointment.

Instructions on how to prepare for skin patch testing will be on your appointment letter. Please follow these instructions carefully and call the hospital if you have any questions or if there’s anything you’re not sure about.

Before your appointment

• Avoid sun exposure, or using sunbeds for one to two weeks before skin patch testing
• Do not use any topical medicines (creams and ointments applied to your skin) on your back and any other area where patches may be applied for at least a week before skin patch testing
• You can use moisturisers up until the day before patch testing but do not apply anything to your skin on the day of your appointment
• Try to avoid taking antihistamines for 48 hours before your appointment 
• If you have hair on your back, please remove this before your skin patch testing appointment

On the day of your appointment

• Ensure the skin on your back is clean, hair free and free of lotions and moisturisers on the day of your appointment

Bring the following with you to your skin patch testing appointment: 

• A list of all medications you are taking including prescribed medications, over-the-counter medicines, and supplements 
• All ointments and creams you use, including those prescribed and bought over the counter 
• Any toiletries such as make-up, creams, lotions, skincare products, hair products and nail polish 
• Any other products that may be triggering your contact dermatitis including household cleaners, washing powders and fabric softeners, (bring the packaging showing the list of ingredients)
• If possible, bring a sample of any products or chemicals you use at work. If this isn’t possible, try to find out its chemical composition and concentration. If you work with industrial chemicals, your company's regulatory affairs or quality control department will have these details.

Skin patch testing usually involves three visits to the clinic over one week.

First, you will have an appointment with the nurse to have the skin patches applied, followed by a second appointment 48 hours later to have the patches removed. Finally, you will have a third appointment with your consultant to check your results and discuss possible treatment options.

During skin patch testing, small aluminium discs (about 1cm in diameter) containing diluted amounts of each substance to be tested will be applied to your back and held in place by hypoallergenic tape. The location of each disc is marked on your skin with ink. This first appointment normally takes around two hours.

The discs usually remain in place for 48 hours. Your skin around the patches may itch during this time which is normal. After 48 hours, you will return to the clinic to have the patches removed. More patches may be applied during your second visit. In some cases, we may need to expose certain areas of your back to ultraviolet (UV) light to see if this triggers a reaction or if certain chemicals cause a reaction when exposed to UV light. This is known as photo patch testing.

After the patches are removed, the ink used to mark the location of each allergen remains on your skin for at least two days. Your third appointment with your consultant is normally 48 hours after your patches have been removed.

Core substances tested include:

• Antioxidants
• Cutting oils
• Epoxy resin systems
• Antibiotics; antiseptics; anaesthetics; corticosteroids and ophthalmics
• Perfumes, flavours
• Plants
• Rubber chemicals
• Textile and leather dyes
• Bakery allergens
• Dental materials
• Hairdressing substances
• Metal compounds
• Photo allergens
• Plastic materials
• Shoe allergens
• Vehicles, emulsifiers
• Cosmetics
• Disinfectants
• Industrial biocides
• Methacrylate
• Photographic chemicals
• Preservatives
• Sunscreen agents

During your skin patch testing week: 

• Avoid getting your back wet including bathing, showering, and swimming. You can have a shallow bath, or a strip-down wash during this time
• Wear old clothes and avoid light-coloured clothes as the ink used to mark your skin may permanently stain your clothing
• Wear an old bra, shirt, vest, or T-shirt at night to protect the patches
• Avoid exposing your back to UV light from the sun or sunbeds
• Avoid participating in sports or any physical activity that may cause you to sweat excessively as this may cause the patches to come off
• If a patch starts to peel off, reattach it using the tape you were given at the clinic. If a whole patch comes off, note the time and date, and take a photo of the area to bring to the clinic
• Contact the hospital if you have any questions or concerns

You may experience mild swelling and itching around the patch sites for a few days after your skin patch testing. If you have a skin condition such as eczema, this may flare up after your procedure. This usually subsides within 24 hours.

How many nights will I need to stay in hospital?

Skin patch testing is performed as an outpatient procedure, meaning you can go home when the procedure is complete.

Will I be able to drive home?

If you feel well enough, you can drive yourself home from the hospital after skin patch testing.

How soon can I go back to work?

You can go back to work as soon as you feel well enough after skin patch testing. This may be the same day or the following day. If you have a very active job that makes you sweat a lot, you may need to take time off work until your skin patches are removed. Excessive sweating can cause the patches to come off and should be avoided while the patches are in place.

How soon can I drive?

Assuming you feel well, you can drive as soon as your skin patch testing procedure is finished.

When will I be back to normal?

Recovery from any medical procedure is different for everyone and depends on several factors including your age, general health and how your skin reacts to skin patch testing. Most people are fully recovered and can resume normal daily activities within a few days of skin patch testing.

Your skin patch tests may be negative, meaning no reaction has occurred. A positive reaction will show as redness, itching, and occasionally raised and blistered skin around the test site. This usually occurs by the third appointment, but occasionally may take longer. If you develop a reaction after your final appointment, take a photo of the skin reaction and contact the hospital.

After examining your skin, your consultant will explain your results to you and discuss possible treatment options.

Skin patch testing is a non-invasive, generally safe procedure, but rarely side effects may occur. Possible side effects of skin patch testing may include:

• Skin reddening and itching - this normally subsides within a few days
• Prolonged or persistent reactions - positive test reactions may continue for a few weeks before gradually disappearing
• Eczema flare-up - a positive patch test may cause a temporary eczema flare-up. This normally subsides within 24 hours
• Pigment changes -  changes in pigment (skin colour) may occur at the patch sites which can last for several months
• Scarring - this is very rare (1 in 10,000 cases)
• Allergy - rarely (1 in 500 cases), you may become allergic to one of the substances applied during patch testing

• Flexible appointment times and locations that are convenient for you
• The freedom to choose which hospital and consultant suit your needs
• Personalised, consultant-led treatment plans tailored to your individual needs
• Comfortable and safe private facilities maintained by expert multidisciplinary teams
• Private ensuite rooms as standard
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• Affordable, fixed-price packages with aftercare included
• Flexible payment options to help you spread the cost of your care

If you would like to see a consultant or learn more about dietetics treatment, book your appointment online today or call a member of our team directly on 0808 189 5499.

Content reviewed by Circle in-house team in June 2024. Next review due June 2027.

Patch Testing British Association of Dermatologists

Patch tests DermNet

PATCH TESTING CAN FIND WHAT'S CAUSING YOUR RASH American Academy of Dermatology Association

Contact dermatitis NHS