Antihistamines and decongestants: what to know

An antihistamine may help sneezing, itching and a runny nose. A decongestant targets stuffiness more directly, but can cause restlessness, a racing heartbeat or raised blood pressure in some people.

Histamine is one of the chemicals released during an allergic response. Antihistamines block its effects; some can make you sleepy, while less-sedating options are often easier to use during the day. Decongestants narrow swollen blood vessels inside the nose. They do not treat itchy eyes or sneezing as directly.

Multi-symptom cold and allergy remedies may contain both medicines plus a pain reliever or cough ingredient. Similar packaging can hide different active ingredients, so read the full label rather than relying on the brand name.

Choose a product for the symptom you actually have and follow its label. Do not combine products until a pharmacist has checked that they do not duplicate an antihistamine or decongestant. Avoid driving if a product makes you drowsy, and avoid alcohol because it can add to sedation.

Check before using a decongestant if you have high blood pressure, heart rhythm problems, glaucoma, thyroid disease, difficulty passing urine, are pregnant, or take prescription medicines. Decongestant nasal sprays used longer than directed can make blockage rebound when the spray wears off.

Get urgent help for trouble breathing, swelling of the lips or tongue, fainting, severe chest pain or a sustained pounding heartbeat. Stop the suspected medicine while arranging urgent assessment unless emergency staff advise otherwise.

Arrange a routine review if congestion persists, keeps returning, disrupts sleep, or needs repeated decongestant use. A clinician can check whether allergy, infection, medication rebound or a structural nasal problem is contributing.

Ask which active ingredient matches your main symptom, whether it interacts with your regular medicines, and whether a non-drowsy antihistamine or a non-drug option would suit your daily routine. Mention any previous palpitations, urinary problems or marked sleepiness with allergy remedies.