Hay fever is also known as pollinosis or seasonal allergic rhinitis. For most people, a single allergen sets their symptoms off at about the same time each year. Spring attacks are usually due to tree pollen (not hay), while grass pollens dominate in the summer and weed pollens in the autumn. Hay fever affects about 20% to 25% of Canadians and the incidence is increasing.
Hay fever is an atopic or allergic disease like asthma. This means the body tends to overreact to certain types of outside particles. One way it overreacts is by releasing histamine, a chemical present in many important animal cells. Histamine is a major cause of the symptoms of hay fever including sneezing, runny nose, and even coughing. Hay fever, like asthma, can be inherited. People inherit the general tendency to be allergic but not always specific allergies. For example, if a mother has hay fever to ragweed, her child is at an increased risk of hay fever, but the child may be allergic to other allergens. Children have a 30% chance of developing hay fever if one of their parents is affected and a 50% chance if both have hay fever.
These are some of the pollens most likely to cause an allergic reaction:
- Spring: tree pollens such as oak, elm, maple, alder, birch, juniper, and olive
- Summer: grass pollens such as Bermuda, timothy, sweet vernal, orchard, and Johnson; and weed pollens like Russian thistle and English plantain
- Fall: weed pollens, especially ragweed
Symptoms and Complications
Most people with hay fever know they have it. The symptoms are unmistakable - runny nose, sneezing, itching, and congestion. Other common symptoms include watery eyes, coughing, headaches, and irritability.
Hay fever usually appears regularly at the same time each year. This is how people can distinguish it from other allergies such as to house dust mites or cat dander. Another difference is while hay fever often causes red eyes, "indoor allergies" tend to leave the eyes alone but can cause minor blockage of the ears, particularly in children.
Making the Diagnosis
An important way to recognize hay fever is to remember exactly when the symptoms appear and disappear. Knowing these dates will give your doctor or allergist vital clues as to what's provoking the symptoms.
Sometimes, your doctor or allergist will recommend skin testing for allergies. With skin testing, small, standardized doses of the most common allergens are gently scraped on the skin. If a small rash and itchiness appears, this indicates an allergy to that substance. Most of these tests are almost painless.
The details of where someone lives and works and when they suffer most should help the allergist make a very short list of possible causes. If none of the skin tests produce results, this may be an indication of some other kind of rhinitis (nasal irritation). These conditions can be confused with hay fever:
- Vasomotor rhinitis - The nasal mucous membrane swells up with increased blood flow, causing runny nose and congestion. There's no known cause. It's not an allergic disease.
- Chronic rhinitis - This may be a prolongation of a common cold or a symptom of another disease such as hypothyroidism (low thyroid hormone).
- Rhinitis medicamentosa - This is caused by overuse of spray decongestants, which may actually increase congestion if used for more than 3 consecutive days.
Treatment and Prevention
Prevention of hay fever may be possible if people learn to control their environment. Someone can help prevent or alleviate symptoms by avoiding exposure to allergens that cause all the miserable sneezing and itching. Here are some helpful tips for hay fever sufferers:
- Keep windows closed and use air conditioning at home and in the car to reduce exposure to outdoor pollens. If using air conditioning, keep the unit on the indoor cycle.
- Limit or avoid doing outdoor activities during peak pollen hours (between 5 a.m. and 10 a.m.). Check daily pollen counts on TV or the internet, or in the newspaper.
- If you are outdoors for extended periods of time, make sure to shower and change clothes and shoes to avoid further contact with residual pollen.
- Don't mow lawns or rake leaves. These activities stir up pollen and mould.
- Don't dry sheets or clothes outdoors; they may trap with pollen and mold.
However, it's not always possible to control the environment or to eliminate or avoid allergens, especially those that are air-borne. Many people need medication treatment for relief. Fortunately, most people respond well to medications. The common treatment for hay fever is antihistamines. These can be taken orally or as nose spray or eye drops. Your doctor or pharmacist can help you choose the medication best suited to your needs. For example, many oral antihistamines are now "non-drowsy." People with certain medical conditions (e.g., glaucoma, prostate problems) should consult with their doctor before using antihistamines. Some products contain antihistamines plus decongestants for symptom relief. Again, advice from a health professional is advisable as people with medical conditions such as high blood pressure and diabetes must use caution with these types of medications.
A corticosteroid nose spray may be recommended by a doctor if antihistamines aren't working. Some people may find that nasal sprays, eye drops, and inhalations containing sodium cromoglycate are effective in preventing hay fever problems if treatment is started before allergy season and used on a regular basis. This type of treatment is usually less effective than antihistamines and corticosteroids. Women who are pregnant or breast-feeding should consult their doctor or pharmacist before beginning treatment for allergies.
If allergen avoidance and medical treatment for hay fever aren't effective, a good option is allergen immunotherapy. Allergen immunotherapy may be referred to as desensitization, hyposensitization, or simply, allergen shots. Small amounts of the allergen are injected regularly, slowly increasing the dosage. The hope is that the immune reaction becomes weaker and weaker. Allergy shots are initially given one or two times each week. After about six months of weekly shots, maintenance treatment is started. Maintenance shots are usually given just once each month. After three to five years, some people are able to stop having shots.
Allergen immunotherapy isn't risk-free. Rarely, the patient may have a system-wide immune reaction called anaphylaxis, which can be fatal. People receiving allergen immunotherapy have to wait in the clinic with a physician present for half an hour after each shot in case there is a reaction. The best time to start desensitization is at the end of the annual allergic period.