What should you know about first line antihistamines?

Histamine is released during many allergic reactions and can cause a runny or blocked nose, itchy eyes, or an itchy throat. Antihistamines block histamine signalling, so they can ease symptoms without removing the trigger. Some are more sedating than others; drowsiness can affect driving, work, and balance. Antihistamines may help with allergic rhinitis, allergic conjunctivitis, pet allergy, and house dust mite allergy, but persistent symptoms may need a different treatment approach.

Choose a product with a pharmacist or clinician if you are pregnant, breastfeeding, treating a child, or living with glaucoma, prostate problems, liver disease, or kidney disease. Check the label before combining cold remedies because more than one product may contain an antihistamine. Take it as directed and avoid alcohol or driving if it makes you sleepy. Reduce exposure to a known trigger where possible: wash bedding regularly for dust-mite allergy and keep pets out of sleeping areas if pet dander is the trigger. A saline rinse may also help a blocked nose.

Call emergency services for swelling of the lips, tongue, or throat, breathing difficulty, faintness, or rapidly worsening symptoms after an exposure. Arrange medical advice when symptoms are one-sided, severe, associated with fever or eye pain, or continue despite correct use. Antihistamines do not replace urgent treatment for a severe allergic reaction. Explore [Itchy Eyes](/symptoms/itchy-eyes/) and [Runny Nose](/symptoms/runny-nose/) for symptom-focused information.

Ask which antihistamine fits your age and health, whether it may cause drowsiness, how long to try it, and what to use if nasal or eye symptoms remain troublesome.