Allergic response produce histamines. These histamines will act on different areas of the body (eyes, throat, nose, gastrointestinal tract, skin or lungs) to produce symptoms of an allergic reaction. The allergic response is not limited to a certain amount of exposure. If the body is exposed to the allergen multiple times the immune system will react every time the allergen is present. The reason why people get allergies is not known. The allergens are not passed down through generations. It is believed if parents have allergies the child is more likely to be allergic to the same allergens. Some common symptoms include
Allergic rhinitis other evidence does not. However, the overall quality of evidence is poor. Allergic rhinitis is the type of allergy that affects the greatest number of people. In Western countries, between 10 and 30 percent of people are affected in a given year. It is most common between the ages of twenty and forty. The first accurate description is from the 10th century physician Rhazes. Pollen was identified as the cause in 1859 by Charles Blackley. In 1906 the mechanism was determined by Clemens von Pirquet. The link with hay came about due to an early (and incorrect) theory that the