LABORATORY TESTING AND TREATMENT DERMATOPHYTIDE REACTIONS AND MOULD INFECTIONS

Allergic Contact Dermatitis

Allergic contact dermatitis is an irritation of the skin caused by a reaction of the body to an allergen.  An allergen is a substance which brings about an adverse reaction in a portion of the population when brought into contact with them, but prompts no response from the balance of the population where identical contact is made. 

Allergic reactions can take place locally or systemically depending on the nature of the contact with the allergen and the severity of the reaction.  In the worst case an allergic reaction can result in anaphylaxis or constriction of the airways.  This module focuses on contact dermatitis, being a local reaction.

Contact dermatitis should be distinguished from irritant contact dermatitis and urticaria.  Contact dermatitis arises some hours after contact with the responsible allergen and settles down over some days provided the skin is no longer in contact with the allergen.  Irritant contact dermatitis is caused by excessive contact with irritants such as soaps, solvents and acids.  Urticaria is also a skin inflammation from which a rash appears within minutes of exposure and fades away within minutes to hours.