How to Stop Steroid Medicines Safely. Chronic Pain Medicines. Cholesterol-lowering Medicines. Digoxin: A Medicine for Heart Problems. Antihistamines are medicines that help stop allergy symptoms. These symptoms include: Itchy eyes.
Runny nose or congestion. Skin rashes such as hives. Path to improved health You can take antihistamines in different ways depending on your symptoms. Ask your doctor which OTC antihistamine is best for you based on your symptoms. Things to consider Like most medicines, antihistamines can cause side effects.
The most common include: Drowsiness. Dry mouth. Blurry vision. Decreased appetite. Feeling nervous, irritable, or excited. Can I take my prescription antihistamine with other medicines? Can I share my prescription antihistamines with friends who have allergies? Questions to ask your doctor Do I need an antihistamine? Can I take one over the counter, or do I need a prescription? Which over-the-counter type of antihistamine is the best for my symptoms?
What are the side effects of this type or brand? How long should I take it? But in allergic people, it is excessive. For example, in people with hay fever, contact with pollen in the nose, throat and eyes triggers the mast cells there to release much more histamine than normal. This excessive release of histamine produces the associated symptoms of itching, swelling, runny eyes, etc.
Antihistamines work by physically blocking the H1 receptors, stopping histamine from reaching its target. This decreases your body's reaction to allergens and therefore helps to reduce the troublesome symptoms associated with allergy.
Antihistamines are also used in the treatment of feeling sick nausea and being sick vomiting. However, the exact way that they ease these symptoms is not fully understood. The brain has several key areas which control vomiting. It is thought that antihistamines block H1 receptors in the area of the brain which creates nausea in response to chemicals in the body.
Some antihistamines may also have what is known as an antimuscarinic effect. This means that the medicine can also block another type of receptor found on the surface of certain cells. If these receptors are affected, you may experience some of the side-effects associated with antihistamines. For example, dry mouth, blurred vision and retention of urine. These effects are mainly caused by the older first-generation antihistamines which are described below. Note : antihistamines should not be confused with H2 blockers which reduce the production of stomach acid.
While both types of medicine block the actions of histamine, they work on different receptors in different systems of the body. Some of these medicines are available to buy over the counter from your pharmacist. Others are only available on prescription. These medicines come in a variety of forms, as mentioned above. Your doctor or pharmacist will advise you on how to take your medication, including what dose and how often.
Read the leaflet that comes with your particular brand for further information. All antihistamines work pretty well to reduce symptoms of allergy. Your doctor or pharmacist may advise or prescribe a particular antihistamine depending on the cause of your allergy and on whether you require a sedating or non-sedating medicine.
For other conditions, specific antihistamines may be used. For example, cyclizine and promethazine teoclate are used for feeling sick nausea and being sick vomiting , not for hay fever. Chlorphenamine is the antihistamine most used in an emergency situation such as anaphylaxis, and may be given by injection in this situation.
An antihistamine tablet typically starts to work within 30 minutes after being taken. The peak of effectiveness is typically within hours after being taken. This can vary depending on the reason for treating you. If you have hay fever you may take the medicine throughout the pollen season. Most people who take antihistamines do not have any serious side-effects.
If side-effects do occur, they are usually minor. The most common are:. For a full list of all the side-effects and possible interactions associated with your medicine, consult the leaflet that comes with your medication. If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme.
You can do this online at www. The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines or any other healthcare products may have caused. If you wish to report a side-effect, you will need to provide basic information about:. Most people can take antihistamines safely. Antihistamines should not be used by people with a rare metabolic disorder called acute porphyria. In addition, they may not be suitable for people with liver or kidney problems.
First-generation antihistamines may not be suitable for men with prostate enlargement benign prostatic hyperplasia. They may also not be suitable for people with raised pressure in the eye acute glaucoma or who are at risk of glaucoma. Women who are pregnant or breast-feeding are usually advised not to take antihistamines. This is because it is not known if they do any harm and studies cannot be done on women in this situation just in case. However, they are not known to cause harm.
If certain conditions such as hay fever or morning sickness make you very unwell in pregnancy, the benefit of treatment may be more than the very small risk of any harm. Be sure not to take too much antihistamine.
Many OTC cold and allergy medicines contain them already. Some prescription medicines do, too. If you take more than 1 of these medicines, you may get much more antihistamine than is good for you. Second-generation antihistamines are less likely to interact with other medicines you are taking. Always talk to your doctor if you take other medicines to make sure they are safe. Talk to your doctor before using a first-generation antihistamine if you have any of the following health problems:. If you have kidney or liver disease, talk to your doctor before taking a second-generation antihistamine.
Last Updated: July 21, This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.
Decongestants are medicines that relieve a congested nose. Visit The Symptom Checker. Read More. Path to improved well being When your body is exposed to allergens allergy triggers , it makes histamines.
First-generation OTC antihistamines These were among the first antihistamines scientists developed. Common kinds include: Loratadine brand names include Alavert, Claritin Cetirizine brand names include Zyrtec Fexofenadine brand names include Allegra Note: Some antihistamines are mixed with other medicines.
How do I safely take OTC antihistamines? Taking more than the recommended amount can be dangerous. Mixing medicines can be dangerous. They may have similar active ingredients that add up to be too much medicine. How can I safely store OTC antihistamines?
Could OTC antihistamines cause problems with any other medicines I take? Talk to your doctor before using a first-generation antihistamine if you have any of the following health problems: Glaucoma. Trouble urinating from an enlarged prostate gland. Breathing problems, such as asthma, emphysema, or chronic bronchitis. Thyroid disease. Heart disease.
0コメント