What is patch testing?

Patch testing is a specialist procedure performed in dermatology settings to determine whether a person is allergic to a specific substance (allergen) that has been in contact with the skin. These chemicals can be found in the house or work environment, and include products such as cosmetics, skincare products, preservatives, rubber, metals, perfumes, etc.

Who can benefit from patch testing?

Patch testing is especially useful for patients with suspected allergic contact dermatitis, a skin condition whereby the immune system reacts to a normally harmless substance, causing symptoms in the manner of:

  • Pruritus (itching)
  • Papules (small bumps)
  • Vesicles (blisters)
  • Oedema (swelling)
  • Fissures (cracks)
  • Erythema (redness)
  • Discharge or oozing

How does our patch testing clinic work?

You will be required to attend two face-to-face appointments and one virtual consultation in the space of a week. Our patch testing clinic is fully nurse-led. A typical patch test clinic operates as follows:

  • First appointment (Wednesday): face-to-face. Duration 30 minutes. Your clinician will ask you a series of questions to determine your medical/dermatology history, list of medications, occupation and any relevant information to establish the suitability for patch testing. Once complete, three patch tests will be placed on your back (preferably) and secured with medical tape.
  • Second appointment (Friday): face-to-face. Duration 30 minutes. The patch tests will be removed from your skin and a first reading conducted. In the case of any positive results, you will be informed and provided with the specific patient information leaflet(s).
  • Third appointment (Monday): Duration 30 minutes. Your specialist will request you to take a photo of the tested area and send it to the following e-mail address. Upon receival, we will then interpret the results and send a full report of your investigation, along with some general skin care recommendations and patient information leaflet(s) concerning any detected allergen(s).

How many allergens do we test for?

We use the TRUE TEST® epicutaneous patch test, which contains 35 allergens and allergen mixes that are responsible for the majority of cases of allergic contact dermatitis:

Panel 1.3

  • Nickel sulfate
  • Wool alcohols
  • Neomycin sulfate
  • Potassium dichromate
  • Caine mix
  • Fragrance mix
  • Colophony
  • Paraben mix
  • Negative control
  • Balsam of Peru
  • Ethylenediamine dihydrochloride
  • Cobalt dichloride

Panel 2.3

  • p-tert-Butylphenol Formaldehyde Resin
  • Epoxy Resin
  • Carba Mix
  • Black Rubber Mix
  • Cl+ Me- Isothiazolinone (MCI/MI)
  • Quaternium-15
  • Methyldibromo Glutaronitrile
  • p-Phenylenediamine
  • Formaldehyde
  • Mercapto Mix
  • Thimerosal
  • Thiuram Mix

Panel 3.3

  • Diazolidinyl Urea
  • Quinoline Mix
  • Tixocortol-21-Pivalate
  • Gold Sodium Thiosulfate
  • Imidazolidinyl Urea
  • Budesonide
  • Hydrocortizone-17-Butyrate
  • Mercaptobenzothiazole
  • Bacitracin
  • Parthenolide
  • Disperse Blue 106
  • Bronopol



  • Get your back wet whilst the patches are in place. You can clean the front of your body in the bath or shower, being really careful that the back remains dry.
  • Engage in strenuous physical activities which may encourage sweating or displace the patch tests.
  • Apply creams or moisturisers to your back, as this will disturb the tests and cause them to peel off.
  • Expose your back to the sun or artificial UV light (sunbeds) throughout the testing period.
  • Take oral steroids for up to four weeks before or during the week of patch testing.


  • Wear soft, loose-fitting clothes, preferably old T-shirts or tops which open at the front, rather than those that need to be pulled over your head.
  • Tape the edges of any patches that begin to come off. Use appropriate surgical adhesive tape that has been formulated for skin contact.
  • Write down the date and time any patch has completely peeled off due to moisture or excessive movement.
  • Contact your GP if you develop a reaction on your back after the patch testing course is complete.
  • Remove the patch tests if they cause unbearable itching or discomfort.
  • Please contact us for advice should you have any questions.

Potential side effects

Adverse events reported are normally mild and localized to the test site. The most common are:

  • Burning
  • Tape irritation
  • Persistent reactions
  • Erythema
  • Changes in pigmentation (hypo- or hyperpigmentation)
  • Itching

If these reactions are severe enough, it may be advisable to remove the patch test panel sooner than 48 hours and initiate treatment with a topical (or systemic) corticosteroid. Please contact us for advice should you develop any concerning side effects. Systemic symptoms such as urticaria (generalised), anaphylaxis, or other type of hypersensitivity reactions are extremely rare. However, several contact allergens can elicit urticaria and respiratory symptoms.


Patch testing should not be conducted in the following cases:

  • Patients with history of severe allergic reaction (systemic and/or local) to any of the allergen components or inactive substances of T.R.U.E. TEST (see list above).
  • Patients with exacerbated symptoms of acute dermatitis involving the back region, including redness, broken and inflamed skin, as the interpretation may be inaccurate or result in a false-negative.
  • Pregnant or breast-feeding women.