| Subject | Contents |
| Definition | A collection of symptoms, predominantly in the nose and eyes, that occur after exposure to airborne particles of dust or dander or to pollens of certain seasonal plants in people that are allergic to these substances (see also allergies; asthma ; allergy to mold, dander, dust ). |
| Alternative Names | Hay fever; Nasal allergies |
| Causes, incidence, and risk factors | Allergies are caused by hypersensitivity of the immune system, leading to a misdirected immune response . The immune system normally protects the body against harmful substances such as bacteria, viruses, and toxins . Allergy occurs when the immune system reacts to substances (allergens) that are generally harmless and in most people do not cause an immune response. Hay fever (allergic rhinitis) involves an allergic reaction to pollen. A virtually identical reaction occurs with allergy to mold, animal dander, dust, and similar inhaled allergens. The pollens that cause hay fever vary from person to person and from region to region. Pollens that are carried by bees from plant to plant are seldom responsible for hay fever because the grains are large and have a waxy coating. Pollens that are carried by the wind are smaller and more often cause hay fever. Examples of plants commonly responsible for hay fever include: trees (deciduous and evergreen) grasses most flowers ragweed In addition to individual sensitivity and geographic differences in local plant populations, the amount of pollen in the air can be a factor in whether hay fever symptoms develop. Hot, dry, windy days are more likely to have increased amounts of pollen in the air than cool, damp, rainy days where pollen is washed to the ground. When an allergen such as pollen or dust is inhaled by a person with a sensitized immune system, it triggers antibody production; these antibodies bind to cells that contain histamine. Histamine (and other chemicals) are released by these cells when the antibodies are stimulated by allergens. This causes itching, swelling of affected tissues, mucus production, muscle spasms , hives, rashes, and other symptoms. Symptoms vary in severity from person to person. Some disorders may be associated with allergies in general, and allergic rhinitis in particular. These include eczema and asthma , among others. Allergies are common. Heredity, environmental conditions, and number and type of exposures may contribute to a predisposition to allergies. |
| Symptoms | coughingheadacheitching of the nose, mouth, eyes, throat, skin, or any area runny nose (rhinitis) smell, impairedsneezing , may be frequent stuffy nose ( nasal congestion )tearing, increasedthroat, sorewheezing |
| Signs and tests | History is important in diagnosing allergic rhinitis, including whether the symptoms vary according to time of day or the season and possible exposures that involve pets, diet changes, or other sources of potential allergens. Allergy testing may reveal the specific allergen (s). Skin testing is the most common method of allergy testing. This may include intradermal, scratch, patch, or other tests. Occasionally, the suspected allergen is dissolved and dropped onto the lower eyelid ( conjunctiva ) of the eye as a means of testing for allergies. There are no specific blood tests that are commonly used to diagnose allergic rhinitis/hayfever. |
| Treatment | The goal is to reduce allergy symptoms caused by inflammation of affected tissues.
The best "treatment" is to avoid what causes your allergies in the first place. (See Prevention.) It may be impossible to completely avoid everything you are allergic to, but you can often take steps to reduce your exposure. Medication options include the following: Short-acting antihistamines, which are generally non-prescription, often relieve mild to moderate symptoms but can cause drowsiness. In addition, these antihistamines can blunt learning in children (even in the absence of drowsiness). An example is diphenhydramine (Benedryl). Longer-acting antihistamines cause less drowsiness and can be equally effective, and usually do not interfere with learning. These medications, which require a prescription, include fexofenadine (Allegra), cetirizine (Zyrtec), and loratadine (Claritin). For people with symptoms not relieved by antihistamines alone, nasal corticosteroid sprays are very effective and safe. These prescription medications include fluticasone (Flonase), mometasone (Nasonex), and triamcinolone (Nasacort AQ). Decongestants may also be helpful in reducing symptoms such as nasal congestion , but should not be used for long periods. Cromolyn sodium is available as a nasal spray (Nasalcrom) for treating hay fever '>hay fever . Eye drop versions of cromolyn sodium and antihistamines are available for itchy bloodshot eyes . The most appropriate medication depends on the type and severity of symptoms. Specific illnesses that are caused by allergies (such as asthma , hay fever '>hay fever , and eczema ) may require other treatments. Allergy shots (immunotherapy) is occasionally recommended if the allergen cannot be avoided and symptoms are hard to control. It includes regular injections of the allergen, given in increasing doses (each dose is slightly larger than the previous dose) that may help the body adjust to the antigen . |
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| Expectations (prognosis) | Most allergies are readily treated. However, treatment only affects that exposure, so subsequent exposures will cause another allergic reaction . Rarely, people may outgrow an allergy as the immune system becomes less sensitive to the allergen . However, as a general rule, once a substance has provoked an allergic reaction it continues to affect the person. Desensitization may cause uncomfortable side effects (such as hives and rash ) and may have dangerous side effects such as anaphylaxis . It often requires years of treatment and is effective in about two-thirds of cases. |
| Complications | discomfort during the allergic reaction disruption of lifestyle (rare) drowsiness and other side effects of antihistamines side effects of other medications (See the specific medication.) anaphylaxis (life-threatening allergic reaction) |
| Calling your health care provider | Call for an appointment with your health care provider if severe symptoms of hay fever occur, if previously successful treatment has become ineffective, or if symptoms do not respond to treatment. |
| Prevention | There is no known way to prevent development of hay fever. Symptoms may sometimes be prevented by avoiding known allergens. Most trees produce pollen in the spring, grasses and flowers usually produce pollen during the summer, and ragweed and other late-blooming plants produce pollen during late summer and early autumn. During the pollen-producing times (pollen season), people with hay fever should remain indoors in an air conditioned-atmosphere whenever possible. For people that are sensitive to certain indoor allergens, dust mite covers for mattresses and pillowcases are recommended, as well as avoidance of culprit pets or other triggers. |
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