Urticaria

Most patients with the acute onset of hives do not require laboratory evaluation. Those patients with chronic urticaria need evaluation. A skin biopsy is sometimes performed on hives lasting longer than 24 hours. This is to rule out a rare disease called urticarial vasculitis that looks like hives but is really caused by inflammation of blood vessels. Typical screening tests include a complete blood count, liver function tests, thyroid function tests, thyroid antibody tests, and anti-nuclear antibody testing for lupus. Patient’s with angioedema that recurs have determinations of various complement levels and function tests. Order serum C4 and quantitative and qualitative assays of C1-INH. Consider referral to an allergist for skin prick and allergy specific IgE antibody tests.

dermagraphism-back

Dermagraphism. Rub the skin of all patients who complain of hives or itching. If the skin welts up in a few minutes the diagnosis of dermagraphism has been confirmed and no further testing is necessary. These patients are well controlled with antihistamines.