Hay fever is a generic term for allergic rhinitis, a seasonal reaction to inhaled plant pollen or molds or a chronic, year-round reaction to a wide spectrum of airborne allergens or inhalants (see table 1). The targets are typically respiratory membranes, and the symptoms include nasal congestion; sneezing; coughing; profuse mucus secretion; itchy, red, and teary eyes; and mild bronchoconstriction.
Table1. Common Allergens, Classified by Portal of Entry
Allergic asthma is a respiratory dis ease characterized by episodes of impaired breathing due to severe bronchoconstriction. The airways of asthmatic people are exquisitely responsive to minute amounts of inhalant allergens, food, or other stimuli, such as infectious agents. The symptoms of asthma range from occasional, annoying bouts of difficult breathing to fatal suffocation. Labored breathing, shortness of breath, wheezing, cough, and ventilatory rales* are present to one degree or another. The respiratory tract of an asthmatic person is chronically inflamed and severely overreactive to allergy chemicals, especially leukotrienes and serotonin from pulmonary mast cells. Other pathologic components are thick mucous plugs in the air sacs and lung damage that can result in long-term respiratory compromise. An imbalance in the nervous control of the respiratory smooth muscles is apparently involved in asthma, and the episodes are influenced by the psychological state of the person, which strongly supports a neurological connection.
The number of asthma sufferers in the United States is estimated at more than 20 million, with nearly one-third of them children. For reasons that are not completely understood, asthma and deaths from it have been increasing over the last 30 years, even though effective agents to control it are more available now than they have ever been before. Surprisingly, asthma is more common in developed regions of the world (the United States and parts of Europe) than in less developed countries in Asia and Africa. It has been suggested that modern insulated buildings have created indoor conditions that harbor higher concentrations of airborne allergens and ozone. This suggests a pronounced influence of environmental factors on the development of allergies and asthma.
Atopic dermatitis is an intensely itchy inflammatory condition of the skin, also known as eczema. Sensitization occurs through ingestion, inhalation, and, occasionally, skin contact with allergens. It usually begins in infancy with reddened, vesicular, weeping, encrusted skin lesions. It then progresses in childhood and adulthood to a dry, scaly, thickened skin condition. Lesions can occur on the face, scalp, neck, and inner surfaces of the limbs and trunk. The itchy, painful lesions cause considerable discomfort, and they are often predisposed to secondary bacterial infections. An anonymous writer once aptly described eczema as “the itch that rashes” or “one scratch is too many but one thousand is not enough.”
