OTC antihistamines: quick guide to choices, effects, and safety

If seasonal sniffles, hives, or itchy eyes are annoying you, an over‑the‑counter antihistamine often fixes that fast. This short guide helps you pick the right OTC option, understand how they work, and avoid common safety traps.

Antihistamines block histamine, a chemical your body releases during an allergic reaction. There are two main types you’ll see in stores: first‑generation (older) drugs and second‑generation (newer) ones. First‑generation drugs like diphenhydramine and chlorpheniramine work well but often cause drowsiness and dry mouth. Second‑generation options such as cetirizine, loratadine, and fexofenadine control symptoms with much less sleepiness and are better for daytime use.

How to pick the right OTC antihistamine

Ask what you need it for. For daytime allergy control—runny nose, sneezing, itchy eyes—choose a second‑generation drug: cetirizine (Zyrtec), loratadine (Claritin), or fexofenadine (Allegra). If you need quick nighttime relief or sleep plus allergy relief, diphenhydramine (Benadryl) works but don’t drive after taking it. For hives, cetirizine or higher doses of loratadine often help better than older drugs.

Consider how fast you want relief. Cetirizine and loratadine usually start in one to three hours and last about 24 hours. Fexofenadine starts in one hour for some people and also lasts a full day. Diphenhydramine works in 30–60 minutes but wears off sooner and causes stronger sedation.

Safety tips and when to see a doctor

Never mix antihistamines with alcohol or other sedatives—you’ll likely become very sleepy and your reaction time will drop. Older adults should avoid first‑generation antihistamines because they raise fall and confusion risk. Many antihistamines are safe in pregnancy, but check with your provider before using any drug while pregnant or breastfeeding.

For kids, follow the dosing on the package or ask a pharmacist—liquid formulas vary by age and weight. If symptoms don’t improve after a week, get worse, or you have breathing trouble, wheeze, tight throat, or swelling of the face or lips, seek immediate medical care—these can be signs of a serious reaction.

Combining an oral antihistamine with a nasal steroid spray often gives better control than either alone for persistent allergic rhinitis. If you need daily control, pick a non‑sedating second‑generation antihistamine and take it regularly rather than as needed.

Finally, if you buy online, use a reputable pharmacy and check expiration dates. Keep a note of what helped and what caused side effects—this makes future choices easier and saves time during doctor visits.

Also watch for drug interactions: some antidepressants and antihypertensives can change how antihistamines feel. Don’t mix first‑generation antihistamines with monoamine oxidase inhibitors (MAOIs) without asking a doctor—side effects can intensify. If nasal congestion is your main issue, adding a decongestant like pseudoephedrine may help, but that raises blood pressure and isn’t right for people with heart disease. Eye drops with antihistamine action (ketotifen) work well for itchy, red eyes and avoid systemic side effects. If you have glaucoma or urinary retention, ask a pharmacist before starting any antihistamine. Write down your regular dose and time taken.