The exact cause of eczema is still not known but eczema can be broadly divided into 2 types allergic (also called extrinsic) and non-allergic (also called intrinsic). Allergic eczema constitutes about 75% cases and is associated with a family history of allergic disorders. It is most commonly due to sensitization to common food and inhalant allergens in early childhood. In case of intrinsic dermatitis the most common trigger is an irritant.

New research suggests that the primary defect in atopic dermatitis is with the (physical) barrier function of the epidermis (upper layer of the skin), leading to the secondary immunologic and inflammatory changes.

Eczema is a multifactorial disease with multiple triggers. The triggers also vary depending on the genetics, age, environment and even the psyche (mindset) of the individual. Important triggers include:

Dry skin (almost universal due to defective barrier function): Climate: Winter, Excess sweating. Long frequent hot showers. Staph infection (and other microbes).

Food allergy in infants.

Irritants: Soaps, Detergents Cigarette smoke Clothing: Wool, Synthetic fibers.

Environmental allergens (house dust mites, pollens, pets).

Emotional stresses (school exams, work pressures, relationship problems).

Iatrogenic - Irritant or allergic contact dermatitis to topical treatment.

Hormonal: Pregnancy and menstrual cycle.