Hay Fever (cont.)

An allergic reaction occurs when the immune system attacks a usually harmless substance called an allergen that gains access to the body. To more simply describe this complex immune process, we will make an analogy to a war within the body. The immune system calls upon a protective substance called immunoglobulin E (IgE) antibodies ("E" for "erythema" or redness) to fight these invading allergic substances or allergens. Even though everyone has some IgE, an allergic person has an unusually large army of these IgE defenders -- in fact, too many for his/her own good. This army of IgE antibodies attacks and engages the invading army of allergic substances of allergens.

As is often the case in war, innocent bystanders are affected in battle. These innocent bystanders are special cells called mast cells. These cells are frequently injured during the warring of the IgE antibodies and the allergic substances. When a mast cell is injured, it releases a variety of chemicals into the tissues and blood, one of which is known as histamine. These chemicals frequently cause allergic reactions. These chemicals are very irritating and cause itching, swelling, and fluid leaking from cells. Through various mechanisms, these allergic chemicals can cause muscle spasm and can lead to lung and throat tightening as is found in asthma and loss of voice.

Any substance can cause an allergy if exposed to a person in the right way. But for all practical purposes and with few exceptions, allergic rhinitis is caused by proteins. Commonly, allergic rhinitis is a result of an allergic person coming in contact several times with protein from plants. Many trees, grasses, and weeds produce extremely small, light, dry protein particles called pollen. This pollen is spread by the wind and is inhaled. These pollen particles are usually the male sex cells of the plant and are smaller than the tip of a pin or less than 40 microns in diameter.

Even though pollen is usually invisible in the air, pollen is a potent stimulator of allergy. Pollen lodges in the nasal lining tissues (mucus membranes) and other parts of the respiratory tract where it initiates the allergic response. Up to 30% of Americans at times suffer from allergic rhinitis. A person is programmed to be allergic by his/her genetic makeup and is destined to be allergic from birth. Approximately one in four people with allergic rhinitis also has asthma.

Source: MedicineNet.com
http://www.medicinenet.com/hay_fever/article.htm