Eczema

The terms eczema and dermatitis are used synonymously. Eczema is not a specific disease entity but a characteristic inflammatory response of the skin to both exogenous and enogenous agents.

Causes

Exogenous:

• Irritant contact eczema is due to detergents, alkalis, acids, solvents and abrasive dust. Strong irritants often cause acute eczema, whereas weak irritants often cause chronic eczema.

• Allergic contact eczema is due to delayed hypersensitivity reaction following contact with antigens or haptens. Previous exposure to the allergen is required for sensitisation. The eczema occurs wherever the allergen contacts the skin. During the acute phase, lesions are marked by oedema, erythema abd vesicle formation. As the vesicles rupture, oozing ensues and papules and plaques appear. In the chronic stage, scaling, lichenification and excoriations predominate. Face, neck and hands are the most common body parts involved. Forehead and ears are commonly affected by hair dyes and shampoos; ears are susceptible to metals from earrings; eyelids are particularly affected by airborne allergens and nail polish; the cheeks and lips are prone to react to facial cosmetics.

Endogenous:

• Atopic eczema is due to a genetic predisposition to form excessive IgE antibodies to inhaled, injected or ingested atigens.

1. Patients with atopic eczema have a tendency to develop other allergic diseases like asthma, allergic rhinitis, hay fever, urticaria, and food and other allergies.

2. More than 95% cases develop before the age of 5 years

3. The cardinal feature of atopic eczema are itch, xerosis, scratching and lichenification.

4. Usually chronic or relapsing. 

• Seborrhoeic eczema often runs in families, and is associated with a tendency to dandruff.

1. Possibly due to excessive growth of fungi of the genus Malassezia (formerly called Pityrosporum).

2. Not a disorder of sebaceous glands

3. High prevalence in HIV - infected persons particularly if CD4 cell count < 400/mm³.

4. Patient has characteristic "seborrhoeic look" - oily skin with patulous, prominent follicular orifices.

5. Involves areas rich in sebaceous glands - scalp, retroauricular folds, eyebrows, nasolabial folds, beard area, interscapular and pre-sternal regions, axillae, pubic region, groin, umbilicus and folds under pendulous breasts.

6. Scalp area - diffusely involved with greasy scales on a dull red background.

7. Intertriginous areas - erythematous scaly lesions or exudative crusted lesions.

8. Eyebrows - fine scaling of eyelid margins.

9. An infantile form, which usually involves the scalp (cradle cap), the face and the diaper area, affects as many as 70% of newborns during the first 3 months of life but usually disappears by 1 year of age.

• Discoid eczmea (nummular eczema) is seen most often on the limbs of elderly males, and is of uncertain aetilogy

• Asteatotic eczema is commonly seen on the lower legs, in hospitalised elderly patients.

• Gravitational (stasis) eczema occurs on the lower legs and is often associated with signs of venous insufficiency.

• Pompholyx (dyshidrotic eczema) describes a form of eczema in which bouts of recurrent vesicles or bullae affect the palms, fingers and soles.