OTC Antihistamine Guide: How to Pick the Right Allergy Pill

Most people grab an OTC antihistamine the minute sneezing starts. That works—if you pick the right one. This quick guide helps you compare options, avoid common mistakes, and know when to see a clinician.

Which types work best?

Antihistamines split into two simple groups: first-generation (older) and second-generation (newer). First-generation drugs like diphenhydramine (Benadryl) act fast but cause drowsiness and grogginess. Second-generation drugs—cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra)—cause less sleepiness and last longer. For daytime use, most people do better with second-generation options.

Onset and duration matter. Diphenhydramine works within 15–30 minutes but wears off in 4–6 hours. Cetirizine and loratadine usually take 1–3 hours and last about 24 hours. Fexofenadine often starts in an hour and also lasts 24 hours. Pick based on how fast you need relief and whether you want once-daily dosing.

How to choose one

Ask yourself: Do I need relief fast or do I need to function all day? If you need immediate help and can rest, diphenhydramine is fine. If you must drive, work, or use machinery, choose cetirizine, loratadine, or fexofenadine. If seasonal allergies flare up every day, a once-daily second-generation drug keeps symptoms controlled with fewer side effects.

Kids and seniors need special care. Pediatric doses differ—always check the label or ask a pharmacist. Older adults are more sensitive to drowsiness and confusion; avoid first-generation antihistamines when possible.

Pregnant or breastfeeding? Talk to your provider. Many clinicians prefer loratadine or cetirizine after the first trimester, but check first.

Watch interactions. Don’t mix antihistamines with alcohol, sleeping pills, or strong sedatives. Certain medications can change how antihistamines work—tell your pharmacist what else you take.

Side effects to expect: mild dry mouth, headache, or slight sleepiness with second-generation drugs. With first-generation drugs, expect heavier sedation, blurred vision, and coordination problems. If you get rapid heartbeat, severe dizziness, or confusion, stop the drug and seek care.

Want to save money? Buying generics is standard and safe. Our site has a short guide on buying generic Zyrtec (cetirizine) that covers prices and safe online options. If you buy online, pick licensed pharmacies and check reviews.

When to see a doctor: if symptoms don’t improve after a week of OTC treatment, if you have breathing trouble, wheeze, or swelling of face/throat, get emergency help—those can be signs of severe allergy or asthma.

Practical tip: pair an oral antihistamine with a saline nasal rinse or an intranasal steroid for stubborn congestion. That combo often beats higher antihistamine doses and keeps side effects low.

Got a specific allergy problem or taking other meds? Use the pharmacy chat or ask your clinician—small details can change which OTC antihistamine is safest for you.