What is Allergy? Causes, Signs and Symptoms, Diagnosis and Treatment.

Allergy occurs when a person’s immune system reacts to substances in the environment that are harmless for most people. These substances are known as allergens and are found in dust mites, pets, pollen, insects, ticks, moulds, foods and some medicines.

A particular antibody called immunoglobin (IgE) causes allergic reactions. Antibodies are released to combat foreign and potentially harmful substances in the body.
IgE is released to destroy the allergen and causes the production of chemicals that trigger the allergic reaction.
One of these chemicals is called histamine. Histamine causes tightening of the muscles in the airways and the walls of blood vessels. It also instructs the lining of the nose to produce more mucus.
There are many types of anti-allergy medications. The choice of medication and how it is given depends on the severity of the reaction.
Long-acting antihistamines, These medications are available over the counter. They are meant to be taken for months at a time, even indefinitely. Most can be taken once a day and last for 24 hours.