CONTACT ECZEMA

Contact eczema is caused by contact of the skin with an irritant or an
allergen.
Chronic irritant contact eczema is caused by excessive, repeated
contact of an irritant with the skin. Vaseline commonly causes "vaseline
dermatitis", which presents with papules and pustules on the lower legs,
often of schoolgirls. Common causes of irritant contact eczema on hands,
arms and legs are excessive use of water, soap (especially if not washed
off properly after use) and detergents, and many types of chemicals (e.g.
alkaline and acid solutions, organic solvents such as alcohol, benzene,
toluene, gasoline). Saliva may cause "lip-licking disease" through
repeated wetting of the skin around the lips.
Acute and chronic allergic contact eczema develop after sensitisation
to an allergen through previous contacts with the same allergen.
In acute allergic contact eczema the contact site shows redness,
small or large blisters which on bursting become oozing red erosive
areas, and finally crusting and scaling. When the allergic reaction is set
off by exposure to sunlight it is a photo-allergic contact eczema. Some
soaps contain photo-allergens which cause these reactions. The history
(e.g. "I have applied betadine dressings on that site") and the usually
sharp margins of the eczema help define the causative allergen.
Chronic allergic contact eczema usually shows a symmetrical
distribution and blurred borders. The skin is usually dry, scaly and shows
lichenification (thickening), often cracks. It can spread to sites distant
from the original contact making it difficult to determine the cause.
Some examples of contact allergens are: occupational (dyes,
preservatives, rubber, bleach, soap, floor wax, nickel, oils, diesel,
fertilisers, pesticides, cement), environmental (plants, spices), medical
(betadine, lanolin, local anaesthetics, menthol, camphor), cosmetic
(perfumes, nail polish, hair-chemicals), clothes or jewellery (chromate,
nickel, rubber, dyes). This list is not complete. Allergy testing may be
done by a dermatologist or allergologist.