Multiple: Hay Fever
Multiple: Hay Fever
Hay fever is a form of allergic rhinitis, or inflammation of the soft tissues lining the nose. It is triggered by plant pollen, most commonly ragweed, tree, or grass pollen in the United States. Hay fever can be either seasonal, meaning that the person has symptoms only during certain periods of the year, or perennial, which means that the person has symptoms all year long. Children are more likely than adults to have perennial hay fever.
Hay fever is often grouped together with eczema and asthma as an atopic disease. Atopy is the medical term for the tendency to develop an allergy. About 20 percent of people with hay fever eventually develop asthma, and some develop eczema as well.
Hay fever is an allergic reaction to tree, grass, or weed pollen that is characterized by a stuffy or runny nose, sneezing, and teary or watery eyes. Some patients also complain of coughing, headaches, fatigue, and drowsiness. Although some patients have relatively mild symptoms that last for only a few weeks and are controlled by medications, others may suffer year round from symptoms and may develop such complications as ear infections or chronic inflammation of the sinuses. The National Institutes of Health (NIH) estimates that hay fever costs the United States about $5.3 billion each year in terms of missed school and work days as well as the direct expenses of diagnosis and treatment.
It is estimated that between 20 and 25 percent of Americans have some form of hay fever, although the severity and the specific triggers vary
from region to region across the United States. It is difficult to determine whether various races or ethnic groups have different rates of sensitivity to pollen because of the variations in climate across the country and the different types of trees and grasses that are present. In general, the hay fever season is shorter in the northern states and longer in the South, particularly along the East Coast.
About 80 percent of people with hay fever develop it before age twenty, with the average age at onset being eight to eleven years. Some doctors think that as many as 40 percent of children may suffer from hay fever at some point in childhood. The symptoms typically become less severe in adult life and may go away completely in some cases.
Boys are more likely than girls to suffer from hay fever. Among adults, however, men and women are equally likely to have symptoms.
The basic cause of hay fever is exposure to plant pollen. The most common sources are plants or trees that are pollinated by the wind rather than by bees or other insects. The reason for this difference is that wind-borne pollen particles are lighter and more likely to remain in the air than the heavier pollen grains produced by flowering plants that depend on insects to carry the pollen from one plant to another. For example, ragweed pollen has been found as high as 2 miles (3.2 kilometers) in the
atmosphere and as far as 400 miles (644 kilometers) out to sea. Common sources of airborne pollen include:
- Trees: birch, alder, willow, oak, ash, elm, poplar, olive, hazel, mountain cedar, and horse chestnut.
- Grasses: ryegrass, Kentucky bluegrass, redtop grass, Johnson grass, Bermuda grass, and timothy.
- Weeds: ragweed, sorrel, mugwort, sagebrush, plantain, and nettle.
Hot, dry, and windy days are more likely to trigger the symptoms of hay fever than cool or rainy days. The pollen count is also likelier to be higher early in the morning than later in the day.
When the pollen from these plants enters the patient's airway and the tissues that line the eyelids, immune system reacts to the pollen as an allergen, a substance that triggers an allergy. The process releases a compound called histamine. Histamine is responsible for the runny nose, itchy and watery eyes, and sneezing that characterize hay fever.
Tips for Minimizing Pollen Exposure
Although it is impossible to avoid airborne pollen completely, people who suffer from hay fever may be helped by the following suggestions:
- Check local news sources for the daily pollen count, and stay indoors during the early morning and evening hours; pollen levels are higher at those times.
- Use a face mask designed to filter out pollen if it is necessary to go outdoors.
- Do not dry clothes outdoors.
- Keep windows closed in the house and car; use the air conditioner to control temperature.
- Take a shower after outdoor activity; wash hair each night to remove pollen before going to bed.
- Minimize exposure to other substances that irritate the nasal passages, including cigarette smoke, chlorine bleach and other household chemicals, insect sprays, wet paint, and strong perfumes.
- Have someone who does not get hay fever do yard work.
- Avoid large fields and grassy areas if possible.
- Consider vacationing at the beach or on a cruise rather than in an inland area.
One approach that usually does not work, however, is relocating to a different part of the country. People who move to get away from a specific type of pollen often develop new allergies within a few years in the new location.
The diagnosis of hay fever is based on a combination of the patient's history and skin tests for specific allergens. It is sometimes difficult to tell at first whether a person has hay fever or the common cold, but in general, the symptoms of a cold get better in a few days or a week. When taking the patient's history, the doctor will ask when the symptoms began; whether the symptoms appear during the same time of the year; whether the symptoms are continuous or off and on; and whether they are worse at specific times of day. In some cases the patient has already noticed that certain activities or places seem to trigger the symptoms.
To perform a skin test, the doctor takes a small amount of material extracted from a specific type of pollen and injects it under the patient's skin or applies it to a tiny scratch on the arm or upper back. If the patient is allergic to the material, his or her skin will develop a wheal, or flat-topped reddish swelling. The skin test cannot be used on patients with eczema, however. These patients can be tested for plant allergies by a type of blood test called a radioallergosorbent test (RAST).
Treatment of hay fever has three parts: avoiding the specific trigger(s); using medications to relieve such symptoms as itching eyes and a runny nose; and taking allergy shots to reduce one's sensitivity to triggers.
Medications that are often recommended for hay fever include:
- Antihistamines. These are drugs that counteract the effects of histamine in causing the watery eyes and runny nose associated with hay fever. Some are available over the counter, while others require a prescription. The older antihistamines often make people drowsy. Thus, patients who use these should not drive or operate machinery while taking them. The newer antihistamines are more expensive but do not make people drowsy as a side effect.
- Decongestants. These are sprays or tablets that clear up congestion in the nose. Most can be purchased over the counter while others require a prescription. People with high blood pressure should avoid oral decongestants because they can raise blood pressure.
- Nasal corticosteroids. These are sprays that reduce the inflammation of tissues associated with hay fever. They may take about a week to start to work but are safe for long-term use.
- Gargling and rinsing out the nasal passages with salt water. There are over-the-counter nasal sprays available for his purpose, or patients can make their own rinse by adding one-quarter teaspoon of salt to two cups of warm water. Salt water works well to relieve nasal congestion in many people.
The prognosis for hay fever varies. People with mild symptoms usually do well with a combination of antihistamines and decongestants used as needed during pollen season. Between 85 and 90 percent of patients who are treated by desensitization (allergy shots) benefit from this type
of therapy. Some patients continue to do well after the shots are stopped but others find that their symptoms return with the next pollen season. In addition, desensitization carries some risk of a severe allergic reaction.
People with hay fever are at increased risk of chronic sinus disorders, nosebleeds, asthma, or ear infections.
The best way to prevent hay fever is to avoid things that trigger it. Some techniques for avoiding or minimizing exposure to ragweed and other pollens are listed in the sidebar. Another preventive approach is desensitization, which is also called immunotherapy. In desensitization, patients are given a series of injections of their specific allergen under the skin, with the concentration of allergen in the shots being gradually increased. It takes an average of eight to twelve months for the patient to see results, however, and the injections must be taken for at least three years and sometimes closer to five years.
Hay fever appears to be increasing in frequency among adults in developed countries, although the reasons for the rise are not yet known. One theory is that adults who get hay fever for the first time were either not exposed to common allergens as children or that they become sensitized to allergens when their immune systems are weakened by a viral infection or pregnancy.
A newer form of treatment for hay fever that shows promise is a vaccine called Pollinex Quattro that was developed in the United Kingdom. Instead of receiving desensitization shots for three to five years, patients using the new vaccine get only four shots—one per week for a month. The vaccine was tested on patients in the United States and Canada as well as Europe in the summer of 2007. Researchers hope that the vaccine could be available as early as 2010 following further clinical trials.
SEE ALSO Asthma; Common cold; Eczema
WORDS TO KNOW
Allergen: Any substance that causes an allergic reaction. Pollen is the allergen that triggers hay fever attacks.
Atopy: The medical term for an allergic hypersensitivity that affects parts of the body that are not in direct contact with an allergen. Hay fever, eczema, and asthma are all atopic diseases.
Chronic: Long-term or recurrent.
Desensitization: A form of treatment for hay fever that involves a series of shots containing the allergen to reduce the patient's sensitivity to that particular trigger. Desensitization is also called immunotherapy.
Histamine: A compound that is released during an allergic reaction.
Rhinitis: The medical term for inflammation of the mucous tissues lining the nose. It can be caused by infections or chemical irritants as well as by allergies.
Wheal: A suddenly formed flat-topped swelling of the skin; a welt.
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