Histamine is a substance produced by the body as part of its defence mechanisms. It is stored in cells called mast cells, in almost all tissues of the body. When the body reacts to a foreign substance (known as an allergen, eg flower pollen), the mast cells stimulated by the allergen release their stores of histamine.
The released histamine then binds to its receptors (H1 receptors), causing a chain reaction that results in allergic symptoms. It causes an increase in blood flow to the area of the allergy, and the release of other chemicals that add to the allergic response.
All this results in the symptoms of an allergic reaction. In hayfever, histamine causes inflammation of the nose, eyes, skin or airways and results in itchy watery eyes, a runny nose, sneezing and nasal congestion.
How does it Work ?
This medicine contains the active ingredient loratadine, which is a type of medicine called a non-sedating antihistamine. It works by preventing the actions of histamine.
Loratadine works by blocking histamine H1 receptors. It does not prevent the actual release of histamine from mast cells, but prevents it binding to its receptors. This in turn prevents the release of other allergy chemicals and increased blood supply to the area, and provides relief from the typical symptoms of hayfever.
Loratadine can also be used to relieve the symptoms of a condition called chronic idiopathic urticaria. This is a chronic itchy rash, similar to nettle rash, but with no apparent cause. Blocking the actions of histamine relieves the itching and reduces the rash associated with this condition.
Loratadine is called a non-sedating antihistamine as it does not enter the brain in significant amounts, and is therefore unlikely to cause drowsiness.
What is it used for?
1- Hayfever (seasonal allergic rhinitis).
2- Hayfever that occurs throughout the year due to allergies, eg pets, dust mites (perennial allergic rhinitis).
3- Ongoing itchy rash with no known cause (chronic idiopathic urticaria).
If you are due to have any skin prick tests to diagnose allergies you should stop taking your antihistamines at least 48 hours before the tests. This is because antihistamines can prevent or lessen the skin reactions that indicate an allergy, and so can make the test results unreliable.
Loratadine tablets are not recommended for children under 12 years of age. Loratadine syrup is not recommended for children under two years of age.
Not to be used in Breastfeeding and Pregnancy
This medicine should not be used if you are allergic to one or any of its ingredients. If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with Clarityn.
Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect. Reported side effects include ; Headache, Nausea and Fatigue.