Seasonal Allergies
Seasonal allergies result from exposure to airborne substances (such as pollens) that appear only during certain times of the year.
Seasonal allergies are common. Seasonal allergies (commonly called hay fever) occur only during certain times of the year--particularly the spring, summer, or fall--depending on what a person is allergic to. Symptoms involve primarily the membrane lining the nose, causing allergic rhinitis, or the membrane lining the eyelids and covering the whites of the eyes (conjunctiva), causing allergic conjunctivitis. (Rhinitis and conjunctivitis may be caused by other disorders (see Section 19, Chapter 221 and Section 20, Chapter 229).)
The term hay fever is somewhat misleading, because symptoms do not occur only in the summer when hay is traditionally gathered and never include fever. Hay fever is usually a reaction to pollens and grasses. Different parts of the country have very different pollen seasons. In the eastern, southern, and midwestern United States, the pollens that cause hay fever in the spring usually come from trees, such as oak, elm, maple, alder, birch, juniper, and olive. In the early summer, pollens come from grasses, such as bluegrasses, timothy, redtop, and orchard grass; in the late summer, pollens come from ragweed. In the western United States, mountain cedar (a juniper) is one of the main sources of tree pollen from December to March. In the arid Southwest, grasses pollinate for much longer, and in the fall, pollen from other weeds, such as sagebrush and Russian thistle, can cause hay fever. People may react to one or more pollens, so a person's pollen allergy season may be from early spring to late fall. Seasonal allergy is also caused by mold spores, which can be airborne for long periods of time during the spring, summer, and fall.
Allergic conjunctivitis may result when airborne substances, such as pollens, contact the eyes directly.
Symptoms and Diagnosis
Hay fever can cause itching of the nose, roof of the mouth, back of the throat, and eyes. Itching may start gradually or abruptly. The nose runs, producing a clear watery discharge, and may become stuffed up. Sneezing is common.
Hay fever causes the eyes to water, sometimes profusely, and itch. The whites of the eyes and the eyelids may become red and swollen. Wearing contact lenses can irritate the eyes further. The lining of the nose may become swollen and bluish red. Other symptoms include headache, coughing, wheezing, and irritability. More rarely, depression, loss of appetite, and insomnia develop.
Many people who have a seasonal allergy also have asthma (which results in wheezing), caused by the same allergens that contribute to allergic rhinitis and conjunctivitis.
The diagnosis is based on symptoms plus the circumstances under which they occur--that is, during certain seasons. This information can also help doctors identify the allergen. The nasal discharge may be examined to see if it contains eosinophils (a type of white blood cell produced in large numbers as a result of an allergic reaction). Skin tests can help confirm the diagnosis and the identity of the allergen (see Section 16, Chapter 185).
Treatment
For allergic rhinitis, antihistamines are usually used first. Sometimes a decongestant, such as pseudoephedrine, is taken by mouth with the antihistamine to help relieve a stuffy nose. Many antihistamine-decongestant combinations are available as a single tablet. However, people with high blood pressure should not take a decongestant unless a doctor recommends it and monitors its use. Nonprescription decongestant nose drops or sprays should not be used for more than a few days at a time, because using them continually for a week or more may worsen or prolong nasal congestion. This reaction is called a rebound effect, which may eventually result in chronic congestion.
Cromolyn, which is available as a nonprescription nasal spray, may be useful. To be effective, it must be used regularly. Its effects are usually limited to the areas where it is applied.
When antihistamines and cromolyn cannot control allergy symptoms, doctors may prescribe a corticosteroid nasal spray. Corticosteroid nasal sprays are very effective, and most have minimal side effects. However, these sprays can cause nosebleeds and a sore nose. Azelastine, an antihistamine taken as a nasal spray, may be effective. But it can cause side effects similar to those of antihistamines taken by mouth, especially drowsiness.
When these treatments are ineffective, a corticosteroid may be taken by mouth or by injection for a short time (usually for fewer than 10 days). If taken by mouth or injection for a long time, corticosteroids can produce serious side effects.
Certain people can benefit from allergen immunotherapy (see Section 16, Chapter 185). They include people who have severe side effects from taking drugs usually used to treat allergic rhinitis, who need to take corticosteroids by mouth to control allergic rhinitis, or who also develop asthma. Allergen immunotherapy for hay fever should be started after the pollen season to prepare for the next season. Immunotherapy is most effective when continued year-round.
For allergic conjunctivitis, bathing the eyes with plain eyewashes (such as artificial tears) can help reduce irritation. Any substance that may be causing the allergic reaction should be avoided. Contact lenses should not be worn during episodes of conjunctivitis.
For allergic conjunctivitis, antihistamines are usually taken as eye drops, although they can be effective when taken by mouth. Usually, nonprescription antihistamine eye drops also contain a drug that causes blood vessels to narrow (a vasoconstrictor) and thus reduces the redness. However, something in the eye drops--the antihistamine or another component--sometimes makes the allergic reaction worse. Also, long-term use of a vasoconstrictor may worsen or prolong the inflammation. Prescription eye drops may be more effective.
Eye drops containing cromolyn, available by prescription, are used to prevent rather than relieve allergic conjunctivitis. They can be used when exposure to the allergen is anticipated. Eye drops containing olopatadine, available by prescription, can be very effective. This drug is an antihistamine and, like cromolyn, inhibits mast cells from releasing damaging substances.
If symptoms are very severe, eye drops containing corticosteroids, available by prescription, may be used as a last resort. During treatment with corticosteroid eye drops, eye pressure should be checked regularly, because use of these eye drops can lead to glaucoma. Eyes should also be checked for infection, because corticosteroids suppress the immune system and thus increase the risk of infection. Use of these eye drops is best supervised by an ophthalmologist. If other treatments are ineffective, allergen immunotherapy may be beneficial.
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