American Medical Association Family Medical Guide - American Medical Association [625]
Airborne allergy triggers
Many microscopic substances—such as plant pollen, animal dander, or the feces of tiny insects called dust mites—can trigger an allergic reaction.
Dander on fur
Pollen
Dust mites
Dander on feathers
Extrinsic allergic alveolitis is the term used to describe a group of allergic lung diseases resulting from exposure to dusts of animal or vegetable origin. Some organic substances—such as barley and sugarcane—used on farms or in industry can cause severe allergic reactions, usually from exposure to molds or fungi. The allergic disorder known as farmer’s lung (occupational lung diseases; see page 645) is caused by frequent exposure to a fungus that grows in moldy hay or grain. People who handle animals or who have frequent contact with birds may have severe reactions to their feathers, saliva, or droppings.
People who already have other types of allergies or who have family members who have allergies are more prone to having airborne allergies. Allergic reactions can occur when airborne allergens come in contact with a person’s skin, eyes, or the mucous membranes of the nose. If the allergic reaction affects the airways of the lungs, causing wheezing and difficulty breathing, the disorder is a respiratory disorder known as asthma (see page 640).
Symptoms
Typical symptoms of airborne allergies include sneezing, a runny and itchy nose, a scratchy or sore throat, and itchy, red, swollen, watery eyes. You may have dark circles under your eyes because congestion in the nose interferes with the blood flow in the veins under the eyes. Some people (especially children) have a permanent crease in their nose or an upturned nose from constantly wiping an itchy or runny nose by pushing the nose upward. In rare cases, heavy exposure (such as to dusts generated during some manufacturing processes) can cause more severe symptoms including fever, muscle aches, fatigue, and symptoms of asthma such as difficulty breathing.
Diagnosis
If you have symptoms only during the spring or fall, you may have hay fever. Symptoms that are present all year are more likely to indicate an allergy to airborne substances found indoors, such as mold, animal dander, or dust mites. Your doctor may use skin tests (see page 912) or a blood test (RAST; see previous page) to determine what allergens are causing your symptoms. The doctor may take a sample of your nasal secretions for examination under a microscope to measure the number of eosinophils in your nose. Eosinophils are a type of white blood cell that increases in number during an allergic reaction. Your doctor may also examine your nose for polyps (see page 634), which can cause symptoms similar to those of allergies.
Treatment
Because pollens and other airborne allergens are hard to avoid, your doctor may recommend over-the-counter antihistamines, which relieve symptoms by blocking the action of the histamine-releasing cells that produce the allergic symptoms. However, to be fully effective, antihistamines have to be taken regularly (usually daily for several years). Some people find the side effects of antihistamines, such as drowsiness and dryness in the nose and throat, more annoying than the allergy.
Other types of over-the-counter drugs may provide some relief. An over-the-counter nasal spray containing the medication cromolyn is about half as effective as prescribed corticosteroid nasal sprays but is much safer to use for long periods. Saline (salt solution) nose sprays can help clear the nose of airborne allergens. Doctors generally do not recommend decongestant nose drops or sprays because they can worsen symptoms, and they need to be taken more and more frequently to get the same effect. Take decongestants only if your doctor prescribes them and then only for short periods.
Hay Fever
Hay fever, or allergic rhinitis, is a type of seasonal allergy caused by contact with the light, easily blown pollen of grasses (such as Kentucky blue-grass), trees (such