Antihistamines

- Control the symptoms of allergies

Antihistamines are most commonly used to control the symptoms of allergies such as hayfever. In these conditions they work by preventing the actions of histamine, which is a substance produced by the body as part of its natural defences. It is stored in cells called mast cells, in almost all tissues of the body, and is released when the body reacts to a foreign substance (known as an allergen).

Hay fever is the common term for allergic rhinitis, an allergic reaction that occurs mainly in the nose and eyes. A variety of substances or allergens may cause allergic reactions, including airborne particles of mold, dander, dust or plant-pollens. An allergic reaction caused by pollen is called hay fever.

People prone to hay fever usually experience it in spring or summer, when pollen counts are high (although some people experience it year-round). The types of pollens that cause hay fever differ between individuals and according to geographic region. Smaller pollens more commonly cause hay fever, and plants that often cause the condition include grasses, trees (evergreen and deciduous), flowers and ragweed.

Pollen count also influences when hay fever symptoms may appear. Dry, hot weather and winds promote a higher pollen count, while damp, rainy weather tends to bring pollen to the ground.

Signs & Symptoms

Hay fever symptoms are caused when a person with a sensitized immune system inhales an allergen, thereby triggering antibody-production. The antibodies bind to mast cells, causing them to release histamine, which in turn leads to hay fever symptoms such as:

- Sneezing
- Runny nose
- Itching nose, eyes, ears or throat (or any area)
- Coughing or wheezing
- Impaired sense of smell
- Stuffy nose (nasal congestion)
- Headache (from blocked sinuses)
- Tearing eyes
- Sore throat.

These symptoms are often more severe earlier in the day.

Disorders associated with allergies include eczema and asthma, among others.

How to Treat Hay Fever

Antihistamines (oral)

The lack of anticholinergic effects in non-sedating antihistamines enables use by a wider range of patients.  Non-sedating antihistamines may occasionally cause confusion and drowsiness in some people - we advise caution when operating machinery, driving or drinking alcohol.  Oral non-sedating antihistamines include:

Cetirizine

Desloratadine

Fexofenadine

Loratadine

Sedating oral antihistamines are only suitable if the potential drowsiness is not a problem for the patient, although some tolerance may develop to this effect. People taking sedating antihistamines should not drive or operate machinery as their reactions can be impaired.  Sedating oral antihistamines include:

Chlorpheniramine

Dexchlorpheniramine

Promethazine

Antihistamines (eye, nose)

Azelastine and Levocarbastine are topical, fast-acting, selective H1-antagonists used for treatment and prevention of hay fever symptoms. They have 12 hour duration of action. Antihistamines liquid products should be shaken before use.

Corticosteroids

Nasal corticosteroid sprays such as Beclomethasone and Fluticasone Propionate are used for prophylaxis and treatment of seasonal allergic rhinitis. The time to onset of action varies, but benefits are generally noted in several days. Antihistamines and/or decongestants may be used initially with the steroid treatment to help relieve acute symptoms.  Check other steroid usage (eg. inhalers), and if recurrent nosebleeds or infection or wound inside the nose.

Mast cell stabilisers

Mast cell stabilisers can be very effective on eye symptoms, although they need to be used 4 times a day for best effect.

Sodium Cromoglycate

Natural Antihistamines Treatments

Solgar Quercetin

Nutralife Perilla 6000 Hayfever Relief

Nutralife Hayfever and Sinus Relief

Related Hay Fever Products from Netpharmacy:

Telfast/allegra 60mg 20 Tabs
Alanase Nasal Spray 50mcg 200 Doses
Claratyne/claritin 10mg 10 Tabs
Polaramine 2mg Tablets 50

See Your Doctor

If you have (or suspect you have) allergies, see your health care provider. He or she will need a history of your symptoms, and may advise allergy testing.

Antihistamines may cause side effects that could worsen conditions such as glaucoma, enlarged prostate gland, retention of urine, or obstruction of the gut, and for this reason they should be used with caution in these conditions.

Antihistamines can be used in children though age limits do apply: hydroxyzine is not recommended for children under six months, and promethazine and alimemazine are not recommended for children under two years.

Antihistamines

Hay fever