Eczema (Atopic Dermatitis)
The term eczema is derived from the Greek, meaning "to boil out." The name is particularly apt since to ancient medical practitioners it may have appeared that the skin was "boiling." Today the usage is rather imprecise since this term is frequently used to describe any sort of dermatitis (inflammatory skin condition). But not all dermatitis is eczematous. All eczematous dermatitis, whether due to a familial atopic dermatitis or an acquired allergic contact dermatitis, has a similar appearance. Acute lesions are composed of many small fluid-filled structures called vesicles that usually reside on red, swollen skin. When these vesicles break, clear or yellowish fluid leaks out, causing characteristic weeping and oozing. When the fluid dries, it produces a thin crust which may mimic impetigo. In older lesions, these vesicles may be harder to appreciate, but an examination of the tissue under the microscope will reveal their presence. Eczematous dermatitis has many causes. One of the most common is a condition called atopic dermatitis. Often those using the term eczema are referring to atopic dermatitis. Although atopy refers to a lifelong inherited (genetic) predisposition to inhalant allergies such as asthma and allergic rhinitis (hay fever), atopic dermatitis is not known at this time to be a pure allergic disease. Atopic patients are likely to have asthma, hay fever, and dermatitis. Atopy is a very common condition, and it affects all races and ages, including infants. About 1%-2% of adults have the skin rash, and it is even more common in children. Most affected individuals have their first episode before 5 years of age. For most, the dermatitis will improve with time. For an unlucky few, atopic dermatitis is a chronic, recurrent disorder.
Other eczematous dermatoses include, but are not limited to, allergic contact dermatitis (cell-mediated allergy to a common substance such as poison oak or nickel), irritant dermatitis (from excessive contact with a harsh chemical substance), fungal infections, scabies infestations, stasis dermatitis, very dry skin (asteatosis), pompholyx (dyshidrosis), nummular dermatitis, and seborrheic dermatitis. The differentiation among these conditions is often difficult and time consuming. In addition, it is not uncommon for atopic dermatitis to coexist with another eczematous dermatitis.
Medically Reviewed by a Doctor on 5/12/2015
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