Nickel allergy

Nature

Nickel allergy or nickel allergic contact dermatitis (Ni-ACD) is a form of allergic contact dermatitis (ACD) caused by exposure to the chemical element nickel. It typically causes a rash that is red and itchy and that may be bumpy or scaly. The main treatment is avoiding contact with nickel-releasing metals, such as inexpensive jewelry.

Source: Wikipedia

Incidence 
In Sweden, up to 20% of women and 1% of men may suffer from nickel allergies. People who handle coins frequently are most affected.
Type 
(G) Very specific problems