Itchy Hives for Weeks? Don't Reach for the Benadryl
- The Review Course in Family Medicine
- 1 day ago
- 2 min read
Some Wheal-ly Great Advice on Chronic Urticaria
If you haven’t seen it in your clinic yet, you will. With no explanation, your patent is suddenly covered in itchy, raised welts. Believe it or not, once it’s chronic, it’s NOT an allergy. According to a 2025 CMAJ article, chronic spontaneous urticaria affects up to 3% of the population and, while it is not a risk for anaphylaxis, it is a chronic autoimmune inflammatory condition that can be incredibly frustrating for patients (and for us when we try to explain it to them).
Before scrolling down, ask yourself: A patient has had daily itchy hives for 8 weeks. They have no systemic symptoms or swelling of the lips or tongue. You recommend Benadryl. What are the three specific lab tests you should order to rule out other causes?
(Shocked we wrote “Benadryl?” Brand names are OK! See the SAMPS Official Instructions. That’s only until 2027, when the SAMPs switch to fully multiple-choice).
Diagnosis: You are looking for itchy hives lasting less than 24 hours, or edema without bruising, occurring over a period of more than 6 weeks.
Complete blood count (on the written SAMPs, though, this is forbidden: list specific indices)
C-reactive protein
Erythrocyte sedimentation rate
Workup: Allergy testing is not routinely indicated. You only need to consider a skin biopsy or C1 esterase inhibitor testing if the diagnosis is uncertain or you suspect something like vasculitis (look for painful hives or bruising).
Treatment: The goal is full symptom control. Start with a second-generation antihistamine taken daily, not just as needed.
Escalation: You can increase the dose up to fourfold (e.g., Cetirizine 40 mg daily).
Flares: You can use Corticosteroids (e.g., Prednisone) for a maximum of 5 days for severe flares, but they don't change the disease course.
Avoid: First-generation antihistamines like Benadryl due to sedation and safety risks. Plus, they’re not effective in this condition.
What if it doesn't work? Refer to a dermatologist or allergist if the diagnosis is unclear or if symptoms aren't controlled after 2 to 4 weeks of optimized (high-dose) treatment. Second-line options they might start include Omalizumab or Cyclosporine.
EXAM TIP: On a SAMP, if you are asked for INITIAL investigations for chronic urticaria, do not write "vitals" or "blood work." You must specify C-reactive protein, or Erythrocyte sedimentation rate to get the marks. Also, C1 is not an INITIAL investigation – it’s for select cases only. The most common marks are lost is not reading the question closely.
Join us at The Review Course where we cover all of these exam quirks and updated content. See you there!
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