The meaning of the word "eczema” can cause confusion. Many people use this word to refer to a common skin condition called atopic dermatitis. When this is the meaning, the words "eczema/atopic dermatitis” may be used.

The word "eczema” also has a more general meaning. Eczema can mean a family of skin conditions that causes the skin to become swollen, irritated, and itchy.

Many skin conditions are considered a type of eczema. Atopic dermatitis is one type. Other types include hand dermatitis, nummular dermatitis, and seborrheic dermatitis. Dandruff is a mild type of seborrheic dermatitis. Diaper rash and the rash that many people get after coming into contact with poison ivy are other types of eczema.

What Causes Eczema?
What causes some types of eczema is clear-cut. One type of eczema, irritant contact dermatitis, develops after frequent exposure to a mild irritant such as a detergent or brief exposure to a strong irritant such as battery acid. Another type, allergic contact dermatitis develops when an allergen (substance to which a person is allergic) touches the skin. Common allergens include poison ivy and nickel. A nickel allergy is actually one of the most common causes of allergic contact dermatitis. Many everyday objects contain nickel, including coins, buttons, jewelry, and eyeglass frames.The exact cause of other types of eczema is not fully understood. Researchers believe that atopic dermatitis develops when many factors combine. These factors include inheriting certain genes, having an overactive immune system, and having something that dermatologists call a "barrier defect.” A barrier defect is a term that means "gaps in the skin.” These gaps allow the skin to lose water too quickly. The gaps also allow germs and other things too small to see with the naked eye to enter the body.

Seborrheic dermatitis is another type of eczema that seems to develop when a number of factors interact. These factors include the person’s genes, yeast that live on human skin, stress, climate, and overall general health. Research shows that seborrheic dermatitis tends to be severe in people who have the human immunodeficiency virus (HIV). This indicates that the person’s immune system plays a role.  How do Dermatologists Diagnose Eczema?
If your dermatologist suspects any type of eczema, the doctor will take a complete medical history, ask about your (or your child’s) symptoms, and examine your (or your child’s) skin. This provides enough information to accurately diagnose many types of eczema.

 Eczema is usually diagnosed through a physical examination. If in doubt, or your      doctor feels that you need further tests, you may be referred to a skin specialist, called a dermatologist. Further tests may include skin biopsy, in which a small sample of the inflamed skin is removed for testing, or patch tests, in which little patches of different substances are stuck to your skin for a few days to see if you react to any of them.

Depending on your pattern of skin symptoms, your doctor will ask about your personal and family allergy history, your history of exposure to irritating chemicals and your contact with potential allergy triggers, such as poison ivy.

In many cases, your doctor can diagnose eczema by examining the skin. If your doctor suspects that allergies are involved, patch testing with various allergenic chemicals (nickel, lanolin, fragrances, etc.) may be necessary.

If there are telltale signs that this is an allergic reaction, your dermatologist may order a test called the "patch test.” Patch testing can help identify everyday substances to which a person is allergic.

Sometimes eczema can be easy to diagnose, but a challenge to treat. Teaming up with a dermatologist can help.

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