Antihistamines are medicines that are commonly used to treat allergic reactions such as hay fever (allergic rhinitis). They may also be used to treat sickness, vertigo and insomnia.
Antihistamines can be used to treat a range of conditions. You might take them to ease allergic reactions. These include:
You may also take some types of antihistamines to help relieve the symptoms of sickness, vertigo and insomnia.
There are two main types of antihistamines, which are described below.
The older types of antihistamines are sometimes referred to as sedating antihistamines. This type of antihistamine can affect your brain, causing you to become drowsy. An example of a sedating antihistamine is chlorphenamine maleate (eg Piriton).
The newer types of antihistamines are sometimes referred to as non-sedating antihistamines. This type of antihistamine has less of an effect on your brain and won’t make you so drowsy. Acrivastine (eg Benadryl) is an example of a non-sedating antihistamine.
Your immune system protects you from harmful substances such as bacteria and viruses. It does this by producing antibodies which help to remove these from your body.
In an allergic reaction, your immune system reacts to a harmless substance such as pollen, because it mistakes it for a harmful one. When this happens, a chemical called histamine is released by your immune system. Histamine is very useful because it helps damaged tissue to heal. However, this process can also cause symptoms such as:
Antihistamines work by blocking the effect of histamine in your body. This helps to prevent inflammation and eases allergic reactions.
If you have a severe allergic reaction, your symptoms may include:
This type of allergic reaction is called anaphylaxis. If you have anaphylaxis, it’s important that you get medical help immediately as it can be very serious. You will be given an injection of adrenaline if you have anaphylaxis. Sometimes an injection of an antihistamine is used in addition to adrenaline.
You can buy some antihistamines from pharmacies without a prescription. Examples include chlorphenamine maleate (eg Piriton), loratadine (eg Clarityn) and cetirizine (eg Zirtek). Some antihistamines are only available on prescription from your GP as they could have side-effects or interactions with other medicines you might be taking.
Depending on what you need antihistamines for; you can take them as tablets, liquids, nasal sprays or a cream. Only use antihistamine creams for a short amount of time as they may cause an allergic reaction. Don’t use antihistamine creams on areas of broken skin, unless your GP has said that you can do so.
If you’re pregnant, it’s recommended that you don’t take antihistamines. This is also true if you’re breastfeeding because antihistamines can get into your breast milk. If you feel you need to be treated with antihistamines while pregnant or breastfeeding, see your GP for advice.
If you have epilepsy, you must get advice from your GP before taking a sedating antihistamine. You should not take this type of antihistamine if you have severe liver disease.
This section doesn’t include every possible side-effect of antihistamines. Always read the patient leaflet that comes with your medicine and ask your pharmacist for advice.
The sedating forms of antihistamines will make you feel very drowsy and can affect your coordination. Therefore, it’s important that you don’t drive or drink alcohol for 24 hours after taking a sedating antihistamine. Alcohol can increase the sedative effect of these types of antihistamines. You should not drink alcohol if you’re taking these antihistamines.
With the newer, non-sedating antihistamines drowsiness is less of a problem.
Side-effects that are more common with the older, sedating antihistamines include:
Other, rare side-effects of antihistamines include:
Children and adults over 65 are more likely to get side-effects.
Check with your GP or pharmacist before you take any other medicines at the same time as antihistamines.
Tricyclic antidepressants interact with antihistamines and can increase the drowsiness side-effect. The antihistamine mizolastine can also interact with some other medicines and may cause a serious abnormal heart rhythm. This medicine is only available on prescription from your GP, who will give you advice if you need to take it.
It’s best not to drink alcohol while taking antihistamines of any type as this will increase the drowsiness side-effect.
Antihistamine medicines are shown in the table below. It’s important to remember that you may not be able to buy some of these medicines over the counter as they may be prescription only.
All medicines have a generic name. Many medicines also have one or more brand name. Generic names are written in lower case, whereas brand names start with a capital letter.
|Generic names||Examples of common brand names|
|acrivastine||Benadryl Allergy Relief|
|cetirizine hydrochloride||Benadryl Allergy Oral Syrup, Benadryl for Children Allergy Solution, Benadryl One-a-Day Relief, Piriteze Allergy, Pollenshield Hayfever Relief, Zirtek Allergy Relief|
|hydroxyzine hydrochloride||Atarax, Ucerax|
|For the eyes and nose|
|antazoline (with xylometazoline)||Otrivine-Antistin (for eyes)|
|azelastine||Optilast (for eyes), Rhinoblast (for nose)|
|epinastine||Relestat (for eyes)|
|ketotifen||Zaditen (for eyes)|
|olopatadine||Opatanol (for eyes)|
|Creams and lotions for the skin|
|diphenhydramine hydrochloride||Benadryl Skin Allergy Relief Cream|
|mepyramine maleate||Anthisan, Wasp-Eze Bites and Stings spray, Wasp-Eze|
|Travel sickness and vertigo/nausea|
|diphenhydramine hydrochloride||Nytol, Nytol One-a-Night|
Reviewed by Kuljeet Battoo, Bupa Health Information Team, June 2014.
For answers to frequently asked questions on this topic, see FAQs.
For sources and links to further information, see Resources.
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