What are antihistamines?
Antihistamines are medicines that relieve the symptoms of allergies. When you have an allergic reaction, your body releases a chemical called histamine, which causes symptoms like sneezing, itching and a runny nose. Antihistamines work by blocking histamine, calming these symptoms down.
What antihistamines are used for
Antihistamines are commonly used for:
- hay fever and other allergies
- hives (urticaria) and itchy skin
- reactions to insect bites and stings
- allergic conjunctivitis (itchy, watery eyes)
Drowsy and non-drowsy types
There are two broad groups. Older antihistamines can make you feel sleepy, which is why some are also used to help with sleep. Newer ones are usually “non-drowsy” and are generally preferred for daytime use, such as managing hay fever while at work. A pharmacist can help you choose.
Using them safely
Antihistamines are available in tablets, liquids, nasal sprays and eye drops. To use them well:
- follow the instructions on the packet or your prescription
- if using a drowsy type, do not drive or operate machinery until you know how it affects you
- tell a pharmacist about other medicines you take, as some can interact
Always read the patient information leaflet.
What antihistamines cannot treat
Antihistamines help with everyday allergy symptoms, but they are not a treatment for a severe allergic reaction (anaphylaxis). If someone has swelling of the face, lips or throat, difficulty breathing, or feels faint, this is an emergency — call 999 immediately.
Common questions about antihistamines
- What are antihistamines used for?
- They are mainly used for allergies — hay fever, allergic reactions, hives and itchy skin, and reactions to insect bites and stings. Some are also used for travel sickness or to help with sleep, though that is a separate use.
- What is the difference between drowsy and non-drowsy antihistamines?
- Older "first-generation" antihistamines can make you sleepy, while newer "second-generation" ones usually do not. For daytime allergy relief, a non-drowsy type is often preferred. A pharmacist can advise which suits your needs.
- Can I take antihistamines every day?
- Many people take a non-drowsy antihistamine daily during allergy season, and this is generally fine. If you find you need them long term or they are not controlling your symptoms, speak to a pharmacist or GP.
- Do antihistamines treat a severe allergic reaction?
- No. Antihistamines help mild to moderate allergy symptoms but are not a treatment for anaphylaxis — a severe, life-threatening reaction. That needs emergency treatment (adrenaline) and a 999 call.