Allergy
u DON’T
BE TRICKED
• Do not select antibiotics for URI-related rhinitis, because such therapy does not reduce symptoms compared with placebo but significantly increases the risk of adverse events. • Do not refer patients with allergic rhinitis for skin testing/immunotherapy without a trial of empiric therapy.
v Test Yourself For the past 2 months, a 30-year-old man has had nasal congestion that began with rhinorrhea, coughing, and sore throat. His only medication is oxymetazoline nasal spray BID. ANSWER: The diagnosis is rhinitis medicamentosa. Stop the topical decongestant and select a short course of prednisone or intranasal corticosteroid.
Urticaria Diagnosis The hallmark of urticaria (hives) is the wheal, a superficial itchy swelling of the skin. Wheals involving the skin around the mouth are considered an emergency, requiring careful observation and investigation for airway obstruction. Concomitant angioedema and urticaria occur in 40% of patients, with another 40% experiencing urticaria alone and 20% developing angioedema but no urticaria. Acute urticaria lasts less than 24 hours but may recur. β-Lactams, sulfonamides, NSAIDs, opioids, insect stings, contrast dyes, latex (including condoms), nuts, fish, and eggs are common causes. Urticaria can also be initiated by pressure, cold, heat, vibration, water, or sunlight. Chronic urticaria is defined as having symptoms most days for >6 weeks. Evaluate most patients with chronic urticaria with a CBC, ESR or CRP, and TSH (higher incidence of hypothyroidism). Lesions persisting >24 hours with purpura/ecchymoses upon resolution are likely due to urticarial vasculitis. In this situation, definitive diagnosis is made by skin biopsy. If urticaria is associated with a travel history and prominent eosinophilia, select parasitic infection.
u DON’T
BE TRICKED
• Do not select ANA testing for acute or chronic urticaria. ST U D Y T A B L E : Differential Diagnosis of Urticaria
If you see this…
Select this…
↑ESR, ↑CRP, lesions persisting >24 hours
asculitic urticaria; perform skin biopsy and obtain serum V complement levels, hepatitis B and C serology, cryoglobulins, and serum protein electrophoresis.
Fever, adenopathy, arthralgias, and antigen or drug exposure
Serum sickness; measure IgE level (elevated).
Features of anaphylaxis, obvious allergen exposure
I mmediate hypersensitivity reaction; treat emergently with epinephrine, corticosteroids, and antihistamines.
Marked eosinophilia
arasitic infection, possibly strongyloidiasis, filariasis, or P trichinosis (especially with periorbital edema).
Therapy Avoid aspirin and other NSAIDs. Select nonsedating antihistamines as first-line therapy. If no response is seen, add an H2-blocker (cimetidine, ranitidine), although evidence for effectiveness is mixed. Doxepin blocks H1, H2, and serotonin receptors and is often effective. Short-term oral corticosteroids are indicated in very symptomatic patients with acute urticaria. Patients who have chronic autoimmune urticaria may require methotrexate, azathioprine, or cyclosporine. 2