Can Cetirizine Cause Diarrhea?
Cetirizine does not commonly cause diarrhea and is not recognized as a significant cause of gastrointestinal adverse effects in clinical practice. The most frequently reported adverse effects of cetirizine are dose-related somnolence, headache, pharyngitis, and dry mouth, but diarrhea is not listed among the common or clinically significant side effects 1, 2, 3.
Evidence from Clinical Trials and Reviews
Comprehensive safety reviews of cetirizine across multiple clinical trials in adults, adolescents, and pediatric patients with allergic disorders consistently demonstrate that the drug is well tolerated, with the primary adverse effect being dose-related somnolence 1.
In a pediatric trial of 209 children aged 6-11 years with seasonal allergic rhinitis treated with cetirizine for 4 weeks, the most commonly reported adverse reactions were headache, pharyngitis, and abdominal pain—not diarrhea—and these occurred at rates statistically similar to placebo 4.
Extensive pharmacological reviews confirm that cetirizine's principal effects are mediated via selective inhibition of peripheral H1 receptors, with negligible anticholinergic activity (though dry mouth can occur) and no significant gastrointestinal motility effects that would predispose to diarrhea 2.
Context for Patients with Gastrointestinal Issues
For patients with a history of gastrointestinal problems, cetirizine remains a safe antihistamine choice, as it does not appear on lists of medications commonly associated with drug-induced diarrhea 5.
The comprehensive review of drug-induced diarrhea identifies over 700 drugs that can cause diarrhea, with the most frequent culprits being antimicrobials, laxatives, magnesium-containing antacids, NSAIDs, prostaglandins, colchicine, antineoplastics, and cholinergic agents—antihistamines like cetirizine are notably absent from this list 5.
Clinical Implications
If a patient on cetirizine develops diarrhea, alternative etiologies should be investigated, including concurrent medications (particularly antibiotics, which cause diarrhea in 25% of cases), dietary factors, infections, or underlying gastrointestinal conditions 5.
Cetirizine's favorable tolerability profile makes it suitable for patients requiring long-term antihistamine therapy, including those with chronic allergic conditions, without significant concern for gastrointestinal adverse effects 1, 2.