--- title: "Antihistamines: Uses & Side Effects | HealthAnswers" description: "Antihistamines are medicines that relieve allergy symptoms such as sneezing and itching by blocking histamine, with drowsy and non-drowsy types available." url: https://healthanswers.co.uk/treatments/antihistamines/ robots: noindex --- # Antihistamines: Uses & Side Effects | HealthAnswers Treatments Antihistamines are medicines that relieve allergy symptoms such as sneezing and itching by blocking histamine, with drowsy and non-drowsy types available. Written by HealthAnswers editorial team Medically reviewed by [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) Reviewed 25 September 2026 ## Quick answer What are antihistamines used for? Antihistamines are medicines that ease allergy symptoms such as sneezing, itching, a runny nose and hives. They work by blocking histamine, a chemical the body releases during an allergic reaction. Some cause drowsiness and some don't, and most are available from pharmacies. General UK health information, not a diagnosis. In an emergency call 999 ; for urgent advice use [NHS 111](https://111.nhs.uk/) (GP out-of-hours in Northern Ireland). On this page 6 sections ## Key facts about antihistamines - Antihistamines relieve allergy symptoms like sneezing, itching and hives. - They work by blocking the effects of histamine. - Some types cause drowsiness; many newer ones do not. - They are also used to help with allergic skin reactions and insect bites. ## 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](https://healthanswers.co.uk/symptoms/runny-nose/). Antihistamines work by blocking histamine, calming these symptoms down. ## What antihistamines are used for Antihistamines are commonly used for: - [hay fever](https://healthanswers.co.uk/conditions/hay-fever/) and other allergies - [hives](https://healthanswers.co.uk/conditions/hives/) (urticaria) and itchy skin - reactions to insect bites and stings - allergic [conjunctivitis](https://healthanswers.co.uk/conditions/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. ## What are the side effects of antihistamines? Side effects depend on the type. Drowsy (older) antihistamines can cause: - sleepiness, and slower reactions, co-ordination and judgement, so do not drive or use machinery after taking them - a [dry mouth](https://healthanswers.co.uk/symptoms/dry-mouth/) - [blurred vision](https://healthanswers.co.uk/symptoms/blurred-vision/) - difficulty peeing Non-drowsy antihistamines can cause: - headaches - a dry mouth - [feeling sick](https://healthanswers.co.uk/symptoms/feeling-sick/) - drowsiness, which is less common but still possible The leaflet in the pack lists every side effect and when to get help. You can report a suspected side effect through the MHRA [Yellow Card scheme](https://yellowcard.mhra.gov.uk/). ## 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. ## ! Important safety information for antihistamines A pharmacist can recommend the right antihistamine for you. Tell them about any other medicines you take and any health conditions. Avoid driving or operating machinery if you take a type that makes you drowsy until you know how it affects you. Antihistamines are **not** a treatment for a serious allergic reaction (anaphylaxis) — for swelling of the face or throat, difficulty breathing or feeling faint, call **999**. ## 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. ## Sources - [NHS — Antihistamines](https://www.nhs.uk/conditions/antihistamines/) ## How we reviewed this page Medically reviewed by the [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) First published 4 March 2026 Medically reviewed 25 September 2026 Next review due 25 September 2029 or sooner if NHS or NICE guidance changes Written by HealthAnswers editorial team. Published by HealthAnswers (Elite Digital AI Solutions Ltd). 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