Patch testing is a diagnostic procedure used to identify contact allergies responsible for eczema and eczematous dermatitis. Adhesive panels containing small amounts of standardised allergens (such as metals, fragrance components, preservatives, cosmetic ingredients, household or workplace products) are applied to the skin, usually on the back, to see whether any of these substances trigger an allergic skin reaction.
During the test, the dermatologist places the patches on the back and leaves them in place for about 48 hours. During this time the area must be kept dry, avoiding heavy sweating or excessive movements that might dislodge the patches. After 48 hours, the first reading is performed: the patches are removed and the skin is examined for redness, papules or blisters.
A second reading takes place at 72 hours, and sometimes later, to detect delayed reactions typical of allergic contact dermatitis. Based on the pattern and intensity of reactions, the dermatologist identifies the allergens responsible for the eczema.
Patch testing is indicated when allergic contact dermatitis is suspected, in chronic or recurrent eczema, or when redness, itching, blisters or scaling appear on areas exposed to metals (e.g. nickel), cosmetics, perfumes, soaps, detergents, gloves, glues, dyes or specific occupational products. It is particularly useful to distinguish irritant eczema from true allergic contact eczema, helping to pinpoint the exact cause of skin inflammation.
Treatment options
At MAVIT Clinic, patch testing is part of a comprehensive diagnostic pathway for eczematous skin diseases. Once the relevant allergens have been identified, the dermatologist can provide a personalised list of substances to avoid, guide the patient in choosing safer cosmetics, cleansers, household and workplace products, and prescribe a targeted treatment plan with topical therapies, systemic medications when needed, and protective skincare strategies.
The key benefit of patch testing is that it does not only treat the visible eczema but helps to reduce or eliminate exposure to the underlying cause, leading to fewer flares, less need for medication and better long-term control. Having patch testing at MAVIT Clinic means putting a clear name on the contact allergy, understanding what triggers the dermatitis and building, together with the dermatologist, a tailored prevention and treatment plan to protect the skin over time.
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