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Importance of Allergy Patch Testing

Allergic reactions to house dust mites can happen immediately or be delayed by several hours causing confusion in identifying the cause of a reaction. Allergy testing can help.

House dust mite allergens can cause double-edged discomfort. Whilst inhaled mite allergens can cause sneezing, wheezing or itching; additional skin contact can result in delayed inflammation called contact dermatitis. Two types of allergy testing, if taken together, can identify the double-edged harm mite allergens can cause. They are skin prick testing and patch testing.

What is the difference between these tests?
Skin prick testing confirms the diagnosis of allergic disease such as asthma, rhinitis, allergic dermatitis or any combination of these conditions. Patch testing is used to identify and measure any delayed reactions to irritants or allergens that come in contact with the outer defences of the body, such as skin. This is a clinical process that usually takes 2 to 4 days. The reason for the long delay is because 30% of allergens don???t test positive until the 4th day.

Why are they both important?
Allergic contact dermatitis is a significant clinical problem in children aged ten years and older. This is the same group of patients identified as bearing-the-brunt of common allergic diseases of asthma, rhinitis and rhinitis, diseases with symptoms that can appear shortly after allergen exposure.

Without allergy testing for both immediate and delayed reactions many patients will fail to understand or recognise the triggers of their symptoms. Their symptoms may blend with each other leaving vulnerable patients unaware of personal triggers. Due to this, they may become distressed and reliant upon drugs as a remedy. This is a scenario that allergists have been warning about for years and is especially critical in developing teen-age children.

How can they become implemented?
Atopic patch testing must be performed in clinical settings by fully trained clinicians according to uniform criteria. Patch test results are affected by corticosteroids (steroid) medication but not by antihistamines, whereas skin prick testing for an immediate allergic reaction, is affected by antihistamines but not corticosteroids.

In a recent study noted in the references, researchers concluded that in testing for the severity of allergic dermatitis, house dust mite allergens should be included in basic patch testing.

Furthermore: atopy patch tests have been used in patients with atopic dermatitis (eczema), eosinophilic esophagitis (acid reflux) and as support for the diagnosis of inhalant and food allergy.


  1. Allergy, the Unmet Need, A report of the Royal College of Physicians Working Party. June 2003, ISBN 1 86016 183 9
  2. 'House dust mites atopy patch testing,an important screening tool for detection of house dust mite allergy', Jasiewicz-Honkisz B., Marcewka I., Targosz K, 'Clinical and Translational Allergy', 2015, 5(Supp 1):019
  3. Allergy Diagnostic Testing: An Updated Practice Parameter, Leonard Bernstein et al, 'Annals of Aller, Asthma, & Immunol', 2008, Vol.100, No 3, Supp. 3, p116
  4. 'The relevance of 7-day patch test reading', Higgins E, Collins P, 'Dermatitis', 2013, 24 (5): p 237-'240
  5. 'Patch testing with contact allergens. Guidelines of the German Dermatologic Society and German Society for Allergy and Clinical Immunology', Axel Schnuch et al. for German Contact Dermatitis Research Group (DKG) 2012
  6. Non IgE - late phase allergic reactions???, Haselden BM, Kay AB, Larche M. Immunoglobulin E-independent major histocompatibility complex-restricted T cell peptide epitope induced late asthmatic reactions. J Exp Med. 1999; 189(12): p1885-1894