May 2025

If you suffer from allergies, selecting the right over-the-counter (OTC) medication can feel overwhelming. The two main types are antihistamines and decongestants, but they work in different ways and have different side effects. Your local pharmacist can help you decide which medication is right for you.

Antihistamines

Antihistamines treat allergy symptoms by blocking histamine, a chemical your immune system makes when exposed to an allergen. Histamine causes itchy eyes, sneezing, and a runny nose.

Some antihistamines (such as chlorpheniramine, clemastine, and diphenhydramine) can cause drowsiness. But other antihistamines, such as cetirizine, desloratadine, and loratadine, are much less likely to do so.

Start taking them a couple of weeks before symptoms start. Since each works differently, if one doesn’t work well for you, try another.

Decongestants

Decongestants help treat a stuffy, blocked nose by reducing the swelling of blood vessels in your nose and airways. Common decongestants include phenylephrine and pseudoephedrine. Sometimes, these are found in OTC products that also contain an antihistamine or pain reliever.

For faster relief, you can try decongestant nasal sprays, but talk to your pharmacist first. Limit your use of these sprays to no more than three days. Otherwise, you risk a rebound reaction where your congestion comes back worse.

You can take antihistamines and decongestants together. You shouldn’t take decongestants if you have high blood pressure, heart problems, or prostate problems. Ask your doctor or pharmacist for an alternative option.