How Allergy Happens: A Short Story
The following story illustrates how one type of allergic condition (seasonal pollen allergy or hay fever) can develop:
It is fall. The days have started to grow shorter and cooler and many types of grasses and weeds produce pollen to make seeds for the next growing season. Over a field of ragweed floats an invisible cloud of pollen grains that are soon carried by the wind to a nearby town. A child who has never before been exposed to this substance goes outside and inhales the pollen.
Because of some defect, or predisposing genetic factor, the child’s immune system overreacts. It produces large numbers of IgE antibodies, all designed to respond to ragweed pollen. These antibodies attach themselves to special cells in the child’s nasal passages and upper respiratory tract. These cells (known as mast cells) contain strong chemicals called mediators. The best-known mediator is histamine. The child has just become sensitized to ragweed pollen.
The following week, when the invisible cloud of pollen descends upon the town, the child inhales ragweed pollen again. This time, proteins from the pollen bind in lock-and-key fashion to the specially designed IgE antibodies sticking out from the surface of the mast cells. This sets off an explosion of sorts, as histamine and other mediators burst from inside the mast cells. Histamine travels in the child’s bloodstream to tiny blood vessels in her nasal passages, airways, and eyes. As a result, her blood vessels began to leak fluid that causes swelling and redness; her eyes become itchy and watery; mucus production increases; and sneezing begins – all classic symptoms of hay fever and re-exposure to an allergen.
The child’s parents become concerned because her nose is running, her eyes are watering, she is itching and sneezing and looks extremely uncomfortable. They suspect allergies but are unsure because she has never had such severe symptoms before. Reluctant to give their child medicine without consulting a health professional, her parents schedule an appointment with the family doctor, who then refers her to an allergist (doctor who specializes in allergies). After going through prick skin testing, it is determined that the child is indeed allergic to ragweed pollen, as well as pet dander and mold spores.
As treatment, the allergist recommends several methods of environmental control (eliminating or reducing the child’s exposure to ragweed pollen, pet dander, and mold spores wherever possible) such as keeping windows in the house closed, using an air filtration device, and staying away from cats, dogs, and feathers. Furthermore,a non-sedating antihistamine is prescribed for the child to take during the allergy season. Finally, the allergist also advises the parents that immunotherapy – or allergy shots – may be helpful if the child’s allergies become more severe, or if the medication does not work.
This information has been approved by David Tinkelman, MD (February 2006).
