Do Not Take Another Dose of Cetirizine Within 24 Hours
The FDA-approved maximum dose of cetirizine is 10 mg in 24 hours for adults, and you should not exceed this limit. 1
Why Cetirizine Won't Help Your Flu Symptoms
Cetirizine is an antihistamine designed to treat allergic conditions—not influenza. The medication works by blocking histamine receptors to relieve symptoms like sneezing, itchy eyes, and runny nose caused by allergies, not viral infections. 2, 3
- Flu symptoms require different treatment: Influenza is a viral respiratory illness that causes fever, body aches, fatigue, and cough—symptoms that antihistamines do not address. 2
- If you have confirmed or suspected influenza and present within 48 hours of symptom onset with fever ≥38°C, antiviral medications like oseltamivir (75 mg twice daily for adults) are the appropriate treatment, not cetirizine. 2
Safety Concerns About Taking Extra Cetirizine
Taking more than 10 mg of cetirizine in 24 hours increases your risk of sedation and other side effects without providing additional benefit for flu symptoms. 2, 1
- Cetirizine causes sedation in approximately 13.7% of patients at the standard 10 mg dose (compared to 6.3% with placebo), and this risk increases at higher doses. 2, 4
- At 20 mg daily, cetirizine has been associated with drowsiness without performance impairment in some studies, but other studies showed performance impairment at 10 mg or higher doses. 2
- The FDA label explicitly states: "do not take more than one 10 mg tablet in 24 hours." 1
What You Should Do Instead
Stop taking cetirizine for flu symptoms and seek appropriate treatment for influenza:
If you have fever ≥38°C, body aches, and respiratory symptoms within 48 hours of onset: Contact your healthcare provider about antiviral treatment (oseltamivir 75 mg twice daily for 5 days). 2
For symptom relief of flu: Use acetaminophen or ibuprofen for fever and body aches, stay hydrated, and rest. 2
If you develop severe symptoms: Shortness of breath, chest pain, confusion, persistent high fever, or worsening symptoms warrant immediate medical evaluation. 2
Common Pitfall to Avoid
Do not confuse allergic rhinitis symptoms (clear nasal discharge, sneezing, itchy eyes) with influenza symptoms (fever, body aches, fatigue, cough). Cetirizine is highly effective for allergic conditions but has no role in treating viral infections like influenza. 2, 3, 5