Diagnosis of Generalized Exfoliative Dermatitis
Blood count may show anaemia, white cell count abnormalities, and eosinophilia. Marked eosinophilia should raise suspicions for lymphoma.

>20% circulating Sézary cells suggests Sézary syndrome

C-reactive protein may or may not be elevated.

Proteins may reveal hypoalbuminaemia and abnormal liver function.

Polyclonal gamma globulins are common, and raised immunoglobulin E (IgE) is typical of idiopathic erythroderma.

Skin biopsies from several sites may be taken if the cause is unknown. They tend to show nonspecific inflammation on histopathology. Diagnostic features may be present however.

Direct immunofluorescence is of benefit if an autoimmune blistering disease or connective tissue disease is considered.