What should you know about nickel allergy test with coin?

Coins differ by country, age, composition and surface wear, so a reaction or no reaction cannot tell you how much nickel is released. Pressure, friction, sweat and dirt can irritate skin independently of allergy. A rash after contact may be allergic contact dermatitis, irritant dermatitis or another skin problem. The direction also works the other way: no rash from a coin does not exclude allergy to a watch, button, buckle or jewellery.

Avoid deliberately pressing a coin to broken, inflamed or sensitive skin. Wash the area gently if you have already tried the test, then use a plain moisturiser if the skin feels dry. Keep a record of which objects touch the rash, how long contact lasts and whether sweat or friction is present. A clinician can examine the distribution and arrange patch testing with standard allergens when appropriate. If inflammation needs treatment, topical corticosteroids may be discussed with a clinician.

Get medical advice for a rash that persists after removing the object, repeatedly returns, blisters, oozes, becomes tender or affects a large area. Seek urgent care for trouble breathing, swelling of the lips or face, faintness, fever or rapidly spreading blistering. Do not keep repeating the coin test while waiting for care.

Ask which contact products to pause, whether patch testing can identify nickel sensitivity, how to protect the skin barrier, and what symptoms would suggest infection rather than allergy.