Know Your Enemy

Every year, an estimated 10 million of us visit the doctor complaining of allergic rhinitis, the most common nasal allergy. The good news is that you don't have to suffer.

Besides the obvious discomfort, seasonal allergies can impact quality of life. Allergies can affect memory and attention, and if left untreated, can lead to ear infections, sinus problems, and asthma.

There are medicines you can take and simple things you can do to protect yourself. But first you need to know what you're up against.

Allergies happen when your immune system -- which normally protects your body against invading agents -- reacts to a false alarm. When an allergic person inhales pollen or mold spores, the immune system falsely identifies these foreign particles as a threat and mobilizes to attack by producing large amounts of antibodies called IgE.

Each IgE antibody is specific for one allergy-producing substance, such as ragweed or oak, and stands guard in nasal and eye tissues.

When the antibody encounters its specific allergen, it signals the body to unleash a host of protective chemicals, including histamine. Within 30 minutes, the small blood vessels in your nose widen and engorge tissues, causing a stuffy nose. Glands act up by producing mucus, resulting in the sniffles. Four to six hours later, additional chemicals and proteins signal other inflammatory cells to join in the action. The result: thick mucus and nasal congestion that can last for 24 hours.

"You can have symptoms all night even if you were exposed in the morning," says Dr. Alkis Togias, associate professor of medicine at the Johns Hopkins Asthma and Allergy Center.