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
William P. Dunbar theories about "hay fever" that were current in the late 1800s. Dunbar determined that it was the dried cat saliva on cat hair that caused the allergic reaction. With regard to grass pollen, Dunbar identified the albumin fraction as the active toxin, discovered changes in the blood that accompanied exposure to the pollen, and was able to grade individual's relative susceptibility to each type of pollen. Much of his work on allergies is summed up in his 1913 publication "The present state of knowledge of hay fever". William P. Dunbar William Philipps Dunbar (1863 in Minnesota – 1922) was an