What is patch testing?

Small amounts of common allergens are applied to the skin using adhesive patches, usually placed on the back/upper arms. The patches contain substances frequently linked to contact allergies, including: Fragrances, preservatives, metals, hair dye chemicals, cosmetics ingredients, rubber and adhesives, household and workplace chemicals, nail acrylates.

The allergens remain in contact with the skin for a period of time (48 hours) to determine whether a delayed allergic reaction develops. During this time one cannot shower/bathe as this would adversely affect the patch test results.

Unlike blood allergy tests, patch testing specifically identifies contact allergies rather than food, airborne, or inhaled allergies.

Conditions commonly investigated

Patch testing may be recommended for patients with: persistent eczema, potential contact dermatitis, unexplained skin rashes, reactions to cosmetics or skincare, suspected workplace-related skin irritation, recurrent facial, hand, or body dermatitis despite regular treatment.

Patients may also be asked to bring their own personal items such as creams, makeup, shampoos, perfumes, or clothing products that could be triggering symptoms.

How the process works

The testing process usually takes place over several appointments during the week:

Referral to Surgical Institute Dublin patch testing via a GP or consultant referral – an appointment will be made for you. It is vital you choose to have testing during a week that is not particularly busy as three appointments are required on three separate days during one week.

  1. Day 1 - allergen panels are applied to the back
  2. Day 3 patch removal & initial reading — patches are removed after approximately 48 hours; the skin is checked for early reactions including irritation
  3. Day 5 final review — a dermatologist performs the final assessment at 96-120 hours; results of potential allergens are discussed and patient information leaflets are provided

Typically, between 40 and 70 allergens may be tested depending on the patient's symptoms and history.

Before and during testing

Patients are generally advised to: keep the back clean and dry, avoid moisturisers before appointments, avoid excessive sweating or strenuous exercise, wear loose-fitting clothing, avoid excessive sun exposure in the weeks before testing, avoid the use of topical steroids on the back in the week leading up to the testing.

The patches must remain dry and in place throughout the testing period for accurate results.

Possible reactions and side effects

Positive reactions are usually mild and appear as small red itchy patches where the allergen has been tested. In some cases, stronger reactions such as blistering or temporary irritation may occur. Rarely, temporary pigmentation changes can develop after a stronger skin reaction.

Benefits of patch testing

Patch testing can help patients: identify hidden allergy triggers, improve long-term eczema management, avoid substances causing skin reactions, reduce flare-ups and chronic irritation, develop targeted skincare and lifestyle changes.

By identifying the exact allergen involved, patients can often significantly improve persistent skin conditions through avoidance strategies and tailored treatment plans.

Frequently asked questions

What are the 'dos and don'ts' during patch testing?

During patch testing you should avoid wetting the patches, excessive sweating, and any activities that could dislodge the patches (such as heavy exercise). You should not apply creams or lotions to the test area. Avoid applying topical steroids to the back and avoid taking oral steroids during the patch test week. Your dermatologist will provide you with detailed instructions at your first visit.

Are there any side effects of patch testing?

Some patients may experience mild irritation or redness at patch sites. Occasionally, a strong positive reaction can cause significant local discomfort such as a patch of active dermatitis or blistering. Rarely, a patch test can cause a flare of pre-existing skin conditions. Serious reactions are uncommon, and you will be monitored throughout the process.

Is there anyone who cannot have patch testing?

Patch testing is generally not recommended during pregnancy, or for those with severe or widespread active eczema/dermatitis on the back. Those who are taking high-dose immunosuppressive medication may also not be suitable. You may also not attend for patch testing immediately after recent sun exposure on the back. Your dermatologist will assess your individual suitability at consultation.

What is the difference between patch testing and blood allergy testing?

Patch testing is used to diagnose allergic contact dermatitis—a delayed allergic reaction that happens when your skin comes into contact with substances such as fragrances, preservatives, metals, or rubber. Blood allergy testing measures allergy antibodies (IgE) in your blood. It is used to identify immediate allergies to things such as pollen, dust mites, pet dander, foods, or insect stings.

How long do patch test results take?

The patch testing process takes place over approximately one week, across three visits. Results and their interpretation are discussed with your dermatologist at the final visit, typically 96–120 hours after the initial application.

Meet our specialists

See all

Centre of excellence

The Surgical Institute Dublin team

Every consultation, procedure, and follow-up at Surgical Institute Dublin is delivered by a specialist consultant.

Patient reviews


  • Surgical Institute Dublin is a very professional organisation providing excellent care in a purpose built facility. I was particularly impressed with the ‘See and Treat‘ consultation process and the exceptional people I encountered there!

    Ciaran Donnellan

  • Fantastic service from start to finish. Was able to book and be seen in short order, which is a rarity in Irish healthcare! Staff were very friendly and welcoming. Overall top quality experience.

    Paul Benson

  • Would highly recommend the new Surgical Institute Dublin! I was very worried about a skin lesion on my head and was amazed at how quickly they got me in for an appointment. The facility is completely modern and state-of-the-art. One of the best facilities in Europe!

    It was incredibly convenient to be able to see a top dermatologist and a plastic surgeon all in the same visit. Fantastic, efficient care.

    Conor Doyle

  • Excellent experience. Very accessible, staff excellent and I was able to get treated straight away after my consultation.

    Andrew Lynam

  • Very easy process from booking to consultation and procedure. Lovely staff, professional and efficient service. Clean and modern facilities. Couldn’t fault the place.

    Brendan Power

  • This see-and-treat service is absolutely fantastic! I was very impressed with the whole experience. Dr Jennifer Boggs and Dr Serena Martin were both kind, lovely and highly professional. I had my full body mole check and a small procedure done in one visit. The service was incredibly efficient. Such a great time saver! All the staff were friendly, smiling and welcoming! Highly recommend!