Role of Ancillary Testing

Bacterial culture is needed if lesions appear impetignized.

To rule out herpes or varicella viral infections, consider viral PCR testing. Tzanck smear or viral culture can be performed but are less commonly used.

KOH preparation (for Tinea infection) or skin scrapings (for scabies) should be performed on skin lesions that resemble these conditions.

Allergy tests, such as oral food challenges, radioallergosorbent tests, and patch testing, may identify specific allergies but are not mandatory for diagnosis.

Skin biopsy and HIV test may rule out conditions that mimic AD.

Serum IgE is elevated in a majority of patients; this test is not needed for diagnosis in routine cases.

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  Use of a scalpel blade to collect scale for a KOH examination

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  Multinucleated giant cell from a Tzanck smear with a herpes infection

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  Patch testing results in a patient with eczema