Evaluation of new-onset urticaria

IgE: immunoglobulin E; NSAID: nonsteroidal antiinflammatory drug.

* Initial laboratory testing includes complete blood count with differential, serum creatinine, erythrocyte sedimentation rate, and complement studies (usually C3 and C4).

¶ Patients with these symptoms should have an appropriate workup for their presentation. Uncommonly, new-onset urticaria is associated with systemic conditions, such as autoimmune thyroid disease (Hashimoto thyroiditis and Graves' disease) or systemic lupus erythematosus; usually, these cause chronic urticaria. New-onset urticaria without additional signs or symptoms of these illnesses does not warrant laboratory evaluation. Refer to related UpToDate content for details.

Δ Commonly used H1 antihistamines include cetirizine in the United States and bilastine in Europe, although there are many others. Antihistamine dosing may be increased at any timepoint if symptoms are uncontrolled with standard doses. Common practice is to increase the standard dose to twice daily (eg, cetirizine 10 mg twice daily), then increase to double the standard dose twice daily (eg, cetirizine 20 mg twice daily). The safety and tolerability of these doses have been demonstrated in studies for chronic urticaria. Refer to related UpToDate content for details.

◊ IgE-mediated reactions should be suspected if urticaria occurs within minutes to 2 hours after exposure to a potential allergen. Common allergens that trigger IgE-mediated urticaria include antibiotics (particularly beta-lactams), certain foods (eg, peanuts, tree nuts, or shellfish), and some types of insects (eg, bees, wasps, fire ants).

§ Earlier referral may be helpful if the patient has symptoms refractory to high-dose antihistamines.