Identifiable causes of urticaria

Category	Specific examples
Infections	Viral Bacterial Parasitic
Medications	Beta-lactam antibiotics Fluoroquinolones Anesthetic muscle relaxants Vancomycin Opioids NSAIDs
Foods and certain food additives	Milk Eggs Peanuts and tree nuts Soy Wheat Fish and shellfish Annatto (natural orange food dye) Carmine red (natural red food dye)
Contact urticaria	Contact allergens (animal saliva, raw foods) Latex allergy (contact or inhaled) Stinging nettle plant
Physical stimuli	Dermatographism Delayed pressure Cold Cholinergic Vibratory Aquagenic Solar Exertion/exercise
Miscellaneous transient causes	COVID-19 vaccines and boosters Stinging and biting insects (yellowjackets, bees, wasps, hornets, fire ants, kissing bugs) Radiocontrast medium Scombroid syndrome
Systemic disorders (rare in those with new-onset urticaria)	Serum sickness or serum sickness-like reactions Cutaneous small vessel vasculitis Mastocytosis Autoimmune conditions (autoimmune thyroid disease, SLE)

This table shows common identifiable causes of urticaria. No cause can be identified in up to half of cases of new-onset urticaria.

COVID-19: coronavirus disease 2019; NSAID: nonsteroidal antiinflammatory drug; SLE: systemic lupus erythematosus.

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