How does one recognize the most common types of dermatitis?

Dermatitis mainly results from one of 3 different causes, each corresponding to a different type of the disease: atopic dermatitis, allergic contact dermatitis and irritant contact dermatitis. They can usually be distinguished on the basis of clinical history:

1. When did the trouble start?
2. Where does occur on the body?
3. What, if anything triggers an acute attack or flare?

The age of the sufferer at onset of the first signs also give some clue as to the type of dermatitis.

Atopic dermatitis

In atopic dermatitis, skin involvement is symmetrical; i.e. the eczema is distributed equally on each side of the body. In infants, it's seen mainly on the head, face (especially the cheeks) and the outside surfaces of the arms and the front of the legs (elbows and knees).

The infant's rash is typically dry, with small, raised bumps ('papules').

In older children, the skin changes are situated more on the limbs than the head, and they tend to show signs of chronic dermatitis (excoriation, lichenification, fissures) and evidence of infection.

Please refer to our 4 case studies on atopic dermatitis ( Nicola, Gregory, Christina, and Oliver ) if you wish to know more about distribution and evolution of the skin reactions.

Contact dermatitis (allergic and irritant dermatitis)

Unlike atopic dermatitis, contact dermatitis develops at the site at which the culprit substance made direct contact with the skin. So, depending on the contact, the distribution may or may not be symmetrical. If the substance is airborne, the distribution will appear on exposed skin areas, such as the face and the backs of the hands. Or the rash can entirely cover both hands, as is the case in latex glove dermatitis sometimes seen in nurses, maybe with a small strip of normal skin where the person wore a ring. Substances are more easily absorbed where the skin is thinnest, so the backs of the hands are more easily affected than the palms, which have a thicker epidermis. The absorption of chemical through the skin is increased by moisture. Thus parts of the body where sweat accumulates, such as the axilla, groin and knee flexure, are more likely to be affected.

See the case study descriptions of Sophie and Karen to learn more about distribution of lesions and prognosis of contact dermatitis.