Eczema laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: Edzel Lorraine Co, D.M.D., M.D.

Laboratory Findings

Electrolyte and Biomarker Studies

• To determine whether an eczema flare is the result of an allergen, a doctor may test the blood for the levels of antibodies and the numbers of certain types of cells.
  • In eczema, the blood may show a raised IgE or an eosinophilia.

• The blood can also be sent for a specific test called Radioallergosorbent Test (RAST) or a Paper Radioimmunosorbent Test (PRIST). In the test, blood is mixed separately with many different allergens and the antibody levels measured.
  • High levels of antibodies in the blood signify an allergy to that substance.

Other Findings

• Another test for eczema is skin patch testing. The suspected irritant is applied to the skin and held in place with an adhesive patch. Another patch with nothing is also applied as a control. After 24 to 48 hours, the patch is removed.
  • If the skin under the suspect patch is red and swollen, the patch test result is considered positive and suggests that the person is probably allergic to the suspected irritant.

• Occasionally, the diagnosis may also involve a skin biopsy which is a procedure that removes a small piece of the affected skin that is sent for microscopic examination in a pathology laboratory.
  • Blood tests and biopsies are not always necessary for eczema diagnosis. However, doctors will at times require them if the symptoms are unusual, severe or in order to identify particular triggers.