Some Causes of Urticaria
Cause | Suggestive Findings | Diagnostic Approach |
|---|---|---|
Acute urticaria | ||
Contact or inhaled allergens (eg, latex, animal saliva, dust, pollen, molds, dander) | Onset within minutes or hours after contact with offending agent | Clinical examination alone Sometimes allergy testing |
Medication/substance effects
| Urticaria within 48 hours of drug exposure Angioedema common with ACE inhibitors | Clinical examination alone Sometimes allergy testing |
Emotional or physical stimuli
| Onset typically within seconds or minutes of offending stimulus | Clinical examination, including reproducible response to suspected stimulus |
Infections | Symptoms of systemic infection* | Testing for specific suspected underlying infection Resolution of urticaria after eradication of the infection |
Ingested allergens (eg, peanuts, tree nuts, fish, shellfish, wheat, eggs, milk, soybeans) | Urticaria within minutes or hours after ingestion of offending agent | Clinical examination Sometimes allergy testing |
Insect bites or stings (Hymenoptera venom) | Urticaria within seconds or minutes after insect bite or sting | Clinical examination alone |
Urticaria with or without fever, polyarthralgias, polyarthritis, lymphadenopathy, proteinuria, edema, and abdominal pain within 7–10 days after parenteral administration of a biologic-based medication or substance | Clinical examination alone | |
Transfusion reactions | Urticaria usually within a few minutes after initiating blood product transfusion (or switching to a new unit of blood product) | Clinical examination alone |
Chronic urticaria | ||
Autoimmune disorders (eg, SLE, Sjögren syndrome, autoimmune thyroid disease, cryoglobulinemia, urticarial vasculitis) | Evidence of systemic autoimmune disease, including hypothyroidism or hyperthyroidism (autoimmune thyroiditis); hepatitis, renal failure, and polyarthritis (cryoglobulinemia); malar rash, serositis, and polyarthritis (SLE); dry eyes and dry mouth (Sjögren syndrome); cutaneous ulcers or hypopigmented lesions after resolution of urticaria (urticarial vasculitis) | Specific to type of autoimmune disease under consideration TSH measurement Thyroid autoantibodies (eg, thyroid peroxidase antibodies, antimicrosomal antibodies) Cryoglobulin titers Serum complement levels (C3, C4, C1q) Rheumatologic serologies (eg, ANA, RF, anti-CCP, anti-SS-A, anti-SS-B, anti-Sm, anti-RNP, anti-Jo-1) Skin biopsy (cryoglobulinemia, urticarial vasculitis) |
Signs of underlying cancer (eg, weight loss, night sweats, abdominal pain, cough, hemoptysis, jaundice, lymphadenopathy, melena) | Specific to the type of suspected underlying cancer | |
Chronic idiopathic urticaria | Occurrence of daily (or almost daily) wheals, and itching for at least 6 weeks, with no obvious cause | Diagnosis of exclusion |
Medications/substance (same as those causing acute urticaria) | Unexplained urticaria in a patient chronically taking prescription, over-the-counter, or herbal drugs | Clinical examination Sometimes allergy testing Resolution with stoppage of offending medication or substance |
Heat or cold intolerance, bradycardia or tachycardia, hyporeflexia or hyperreflexia | Clinical examination Usually TSH measurement | |
Physical stimuli (same as those causing acute urticaria) and sometimes emotional exacerbation of urticaria | Urticaria typically within seconds or minutes of offending stimulus | Clinical examination, including reproducible response to suspected stimulus |
Systemic mastocytosis (urticaria pigmentosa) | Presence of small pigmented papules that turn into wheals with mild trauma (eg, gentle stroking) Possible concomitant anemia, abdominal pain, easy flushing, and recurrent headaches | Skin biopsy Serum tryptase level |
* Patients should be asked about recent travel to a developing country. | ||
ANA = antinuclear antibodies; CCP = anticyclic citrullinated peptide; CMV = cytomegalovirus; EBV = Epstein-Barr virus; RF = rheumatoid factor; SLE = systemic lupus erythematosus; TSH = thyroid-stimulating hormone. | ||