How is eczema (atopic dermatitis) diagnosed?

In order for eczema to be diagnosed, a doctor will perform a physical examination and a visual inspection of the patient’s skin. A personal history of any inhalant allergies (hay fever and asthma), as well as a family history of allergies, will also help in making the diagnosis. Bear in mind, itching is not always sufficient evidence for atopic dermatitis to be diagnosed, however, examining itchy eruptions is still necessary.

Some of the major features of atopic eczema/dermatitis that a doctor will look for include:

• A characteristic eczema rash in the areas where the condition typically occurs (i.e. behind knees and arm folds)
• Signs of itching
• Repeatedly or chronically occurring symptoms
• A family or personal history of atopic conditions include eczema, asthma and hay fever

A doctor may also perform a skin biopsy. This test analyses a small skin sample taken from the patient which is then sent to a lab for analysis under a microscope. A number of patients suffering from more severe atopic dermatitis tend to have an elevated number of white blood cells (known as eosinophils) present in their blood. This elevation of white blood cells gives an indication of antibodies being present in the body in response to the immune system attempting to fight off pathogens. These kinds of tests can aid in the diagnosis of atopic eczema.

Additionally, the doctor may also conduct a skin swab, this is done with a long cotton applicator, resembling that of an earbud or Q-tip. This sample will be sent to a lab so as to exclude any staphylococcal infections that may result in symptoms similar to those of eczema or complicate the symptoms of atopic dermatitis.

Prick tests, also known as skin scratches which involve pricking or scratching the skin with a needle containing a very small amount of the suspected allergen may also be conducted. However, these tests, as well as blood tests, are not always useful when diagnosing airborne allergens associated with atopic dermatitis as the results can be difficult to interpret.