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.
Your doctor would talk this over with you and prescribe one of the antihistamines believed to be safe in pregnancy if you choose to take one. Similarly, in breast-feeding women, in some cases the benefits may be more than the risk. Antihistamines do come through in small quantities into breast milk, although they are not known to cause any harm. A full list of people who should not take antihistamines is included with the information leaflet that comes in the medicine packet.
If you are prescribed or buy an antihistamine, read this to be sure you are safe to take it. Usually it is possible to find an antihistamine which keeps your symptoms controlled. Sometimes you may need to experiment and try more than one to find the one that works best for you. Antihistamines are generally more effective when taken constantly rather than intermittently.
This is particularly applicable for people with hay fever seasonal allergic rhinitis. In the summer months the pollen count is generally higher and you may be in contact with the allergen on a regular basis. You can buy many different brands and forms of antihistamines without a prescription. Some work for only 4 to 6 hours, while others last for 12 to 24 hours.
Some are combined with a decongestant, a drug that dries up your nasal passages. Some antihistamines cause less sleepiness than others. These include cetirizine Zyrtec , desloratadine Clarinex , fexofenadine Allegra , and loratadine Claritin. Do not drink alcohol when you are taking antihistamines. Also, remember: Store antihistamines at room temperature, away from heat, direct light, and moisture. Do not freeze antihistamines.
Keep all medicines where children cannot reach them. Side Effects of Antihistamines. Antihistamines are thought to be safe for adults. Most antihistamines are also safe for children over 2 years old. If you are breastfeeding or pregnant, ask your provider if antihistamines are safe for you. Adults who take antihistamines should know how the medicine affects them before driving or using machinery. If your child is taking antihistamines, make sure the medicine is not affecting your child's ability to learn.
There may be special precautions for using antihistamines if you have: Diabetes Enlarged prostate or problems passing urine Epilepsy Heart disease or high blood pressure Increased pressure in the eye glaucoma Overactive thyroid Side effects of antihistamines may include: Changes in vision, such as blurry vision Decreased appetite Dizziness Drowsiness Dry mouth Feeling nervous, excited, or irritable.
When to Call the Doctor. Call your provider if: Your nose is irritated, you are having nosebleeds, or you have any other new nasal symptoms Your allergy symptoms are not getting better You are having trouble taking your antihistamines. Mixing benadryl and alcohol has several distinct dangers to be….
Allergic reactions are numerous and varied, and the best treatments depend on the specific symptoms, such as rashes or sinus problems, and their…. In this article, learn about what eye drops are available for itchy eyes, when eye drops should be used, and when people should see a doctor. An allergy develops when the immune system becomes hypersensitive to a food or other substance. Learn how to identify and manage allergies here.
What are antihistamines? Medically reviewed by Alan Carter, Pharm. Overview Symptom relief Types Side effects and risks Summary We include products we think are useful for our readers. What are they, and how do they work? Share on Pinterest A person may take antihistamines to treat allergic rhinitis. What symptoms do they treat? Side effects and risks. Exposure to air pollutants may amplify risk for depression in healthy individuals.
Costs associated with obesity may account for 3. Related Coverage. Zyrtec vs. Claritin for treating allergies. Medically reviewed by Dena Westphalen, Pharm. Can you drink alcohol while taking antihistamines? Medically reviewed by Alan Carter, PharmD.
How do you treat an allergic reaction?
0コメント