Seasonal allergies result from exposure to airborne substances (such as pollens) that appear only during certain times of the year.
Seasonal allergies (commonly called hay fever) are common. They 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 (see Allergic Conjunctivitis).
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. The pollens that cause hay fever vary by season:
Also, different parts of the country have very different pollen seasons. 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 weeds, such as sagebrush and Russian thistle, can cause hay fever. People may react to one or more pollens, so their 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.
Hay fever can make the nose, roof of the mouth, back of the throat, and eyes itch. Itching may start gradually or abruptly. The nose runs, producing a clear watery discharge, and may become stuffed up. In children, the stuffy nose may lead to an ear infection. The lining of the nose may become swollen and bluish red.
The sinuses may also become stuffed up, causing headaches and occasionally sinus infections (sinusitis). Sneezing is common.
The eyes may water, sometimes profusely, and itch. The whites of the eyes may become red, and the eyelids may become red and swollen. Wearing contact lenses can irritate the eyes further.
Other symptoms include coughing, wheezing, and sometimes irritability and trouble sleeping.
The severity of symptoms varies with the seasons.
Many people who have allergic rhinitis also have asthma (which results in wheezing), possibly caused by the same allergy triggers (allergens) that contribute to allergic rhinitis and conjunctivitis.
The diagnosis is based on symptoms plus the circumstances in which they occur—that is, whether they occur only during certain seasons. This information can also help doctors identify the allergen.
Typically, no testing is necessary, but occasionally, the nasal discharge is examined to see whether it contains eosinophils (a type of white blood cell produced in large numbers during an allergic reaction). Skin tests can help confirm the diagnosis and identify the allergen (see Diagnosis).
A corticosteroid nasal spray is usually very effective and is used first. Most of these sprays have few side effects, although they can cause nosebleeds and a sore nose.
An antihistamine, taken by mouth or used as a nasal spray, can be used instead of or in addition to a corticosteroid nasal spray. Antihistamines are often used with a decongestant, such as pseudoephedrine, taken by mouth. Many antihistamine-decongestant combinations are available over the counter as a single tablet. However, people with high blood pressure should not take a decongestant unless a doctor recommends it and monitors its use. Also, people who take a monoamine oxidase inhibitors (a type of antidepressant) cannot take a product that combines an antihistamine and a decongestant.
Decongestants are also available over the counter as nose drops or sprays. They 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—called a rebound effect—and may eventually result in chronic congestion.
Antihistamines may also have other side effects, particularly anticholinergic effects. They include sleepiness, dry mouth, blurred vision, constipation, difficulty with urination, confusion, and light-headedness.
Side effects tend to be fewer and less severe with nasal sprays than with drugs taken by mouth.
Other drugs are sometimes useful. Cromolyn is available by prescription as a nasal spray and may help relieve a runny nose. To be effective, it must be used regularly. Azelastine (an antihistamine) and ipratropium, both available by prescription as nasal sprays, may be effective. But these drugs can have anticholinergic effects similar to those of antihistamines taken by mouth, especially drowsiness.
Montelukast, a leukotriene modifier available by prescription, reduces inflammation and helps relieve a runny nose. But how it is best used has not been established.
Regularly flushing out the sinuses with a warm water and salt (saline) solution may help loosen and wash out mucus and hydrate the nasal lining. This technique is called sinus irrigation.
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 have serious side effects.
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.
Eye drops containing antihistamines and a drug that causes blood vessels to narrow (a vasoconstrictor) are often effective. These eye drops are available without a prescription. However, they may be less effective and have more side effects than prescription eye drops (see Diagnosis and Treatment). 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. If symptoms are very severe, eye drops containing corticosteroids, available by prescription, may be used. During treatment with corticosteroid eye drops, the eyes should be checked regularly for increased pressure and infection by an ophthalmologist.
Allergen immunotherapy (desensitization):
If other treatments are ineffective, allergen immunotherapy helps some people (see Allergen immunotherapy (desensitization)). Immunotherapy is needed in the following situations:
Allergen immunotherapy for hay fever should be started after the pollen season to prepare for the next season. Immunotherapy has more side effects when started during pollen season because the allergens have stimulated the immune system. Immunotherapy is most effective when continued year-round.
Last full review/revision May 2014 by Peter J. Delves, PhD