About Eczema: Causes
Genetic inheritance plays a major role in most forms of eczema. Atopic dermatitis is an inherited oversensitivity of the immune system. Genes play a role in allergies, too, though it usually takes prolonged exposure to a given allergen before it becomes a nuisance. There are some chemicals, of course, that will irritate any skin. Harsh irritants can give anyone a temporary bout of contact dermatitis.
Seborrhea appears to be linked to the yeast called Pityrosporum ovale, which inhabits most human scalps. It's a mystery why some people are so much more severely affected by this organism than others.
Varicose eczema is caused by poor circulation in the lower extremities. Fluid builds up in the capillaries due to raised blood pressure. This causes inflammation of the skin.
Lichen simplex is caused by excessive scratching of minor itches.
There are also general risk factors than will aggravate any kind of eczema. These include harsh soap, rubber gloves, wool, very hot water, and emotional stress.