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The intensity of the symptoms varies from person to person and from season to season depending on the amount of pollen. Some people manage with no medication while others find relief by occasional or more frequent use of antihistamines available at the local pharmacy. Many patients have such severe symptoms that their daily activities are disrupted.
An allergy is a reaction by the body’s immune (defense) system to chemical triggers in the environment called allergens. The linings of the nose, eyes and bronchial tree become irritated by repeated exposure to an allergen such as grass pollen or cat dander. The body responds by releasing a protein called immunoglobulin-E (Ig E). The Ig E starts a chemical chain reaction causing tissues to become swollen and inflamed, leading to the itch and the watery secretions.
Five to 15 per cent of the population have allergies. The symptoms most often begin in childhood and early adulthood but may first occur at any time in life. If there is a family history of allergies, especially in parents, the risk of the children also having allergies is four times higher.
Foods - Allergy to foods is particularly important in babies. A baby’s intestinal tract takes time to develop and mature. If a food protein is introduced too early, the lining of the intestine may become sensitized. Cow’s milk can cause early symptoms such as colic. Prevention of allergies is one of the important advantages of breast feeding. Seven months may be an acceptable period to introduce meats although where there is a family history of allergy, this should be delayed until the first birthday. Corn, eggs, wheat and fish should be held off as long as possible and, where there is a family history of allergy, to a minimum of one year. Shellfish should not be introduced before the first birthday.
Peanuts can cause a serious allergic reaction called anaphylaxis. Children younger than three years should never be given peanuts. Waiting will reduce the risk of developing a peanut allergy. A child with a peanut allergy must be taught never to eat another child’s sandwich, cookies or candy bar. Schools are more aware of this problem although few have been willing to make the school peanut-free. Children with a peanut allergy must have an adrenaline emergency kit (ANAKit, EPIPen) available for immediate use and teachers should be taught how to use them. Airline travel can be a problem because peanuts are often served and even the peanut chemical in the air can trigger a reaction.
The Food Allergy Network from the United States provides regular bulletins on products containing common allergies such as milk, eggs or peanuts.
Animals - Household pets, especially cats, are a common source of allergies. The cat allergen (FELd1) can be given in a serum as an injection (allergy shot). Cat allergen can be found in homes even months after the cat has been removed, on the clothes of cat owners and especially in carpets. Children exposed to household pets can develop allergy symptoms at an early age. Dogs, birds, guinea pigs, hamsters, rabbits and now ferrets are other favourite pets that can be sources of allergy symptoms.
Dust mites – these are microscopic animals that produce droppings that cause dust allergy. They live in peoples’ homes in warm, humid climates and feed on skin residue in mattresses and carpets. Dust mites are less common in dry climates such as Alberta but have been found in some homes with high humidity where they have been brought in from other regions on clothing. Dust allergy can be controlled by allergen-proof mattress coverings and by washing nightwear and bedding at high temperature. Dust mites are a major cause of asthma. Asthma control can be easier in children who have mite-free bedrooms.
Insects - Cockroaches are an important cause of asthma. They are common in large cities, especially in older multilevel housing. Their control and extermination is extremely difficult. Allergy to stinging insect venom (bees, hornets, wasps) can cause anaphylaxis and death. People with these allergies should receive a potentially lifesaving treatment with allergy shots. Mosquitoes rarely cause more than an irritating reaction.
Moulds - Moulds are a common allergen. Indoor moulds are found in humid homes - primarily in household plants, dried flower arrangements, bathroom, laundry rooms, mud rooms, humid basements, humidifiers and under sinks. Damp windows in winter can lead to black mould on the frames. Leaky roofs or walls may also be a source. Outdoor molds are found in grass clippings, piles of leaves and dense vegetation. High mould counts occur in all parts of the country. Peak mould seasons are spring and fall.
Pollens - As noted above, tree, grass and ragweed pollen are the prime source of seasonal allergy symptoms, commonly called hayfever. The types and quantities of pollen vary from season to season and in various parts of the country. Most patients know the season by the type of allergy symptoms they have.
Many people will say, “I know what my allergies are,” and buy over-the-counter medications to treat themselves. This may work for some people but is not always the best approach. Sometimes treatments have been only partially effective. Complications such as sinusitis or ear infections may arise. Asthma may go undetected. Your family doctor or an allergist may help to recognize and prevent possible serious effects of allergies.
First, the doctor will take a full history including information about childhood infections, frequent coughs and colds, early symptoms of asthma, relevant family history and environmental factors. Other factors such as cigarette smoke and industrial exposures can be relevant.
Sometimes further information is needed. Your family doctor may need to perform skin testing or refer you to an allergist for testing. This would be done to identify those allergens that your symptoms. After the results are explained, appropriate treatment is discussed.
Skin testing has been well-researched. The 'prick' method is recognized as the best allergy test by the Canadian Society of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology. A drop of allergen is placed on the forearm and the skin is pricked through the drop. The allergen used should be recognized, tested and approved by the Health Protection Branch of the Federal Government. The number of tests performed is decided by the allergist after taking a thorough history of the condition.
In 15 to 20 minutes, the testing sites are examined or 'read.' A wheel 'bump' means an allergic reaction. The reaction at the test site is compared in size to one using a control solution to determine the degree of sensitivity. A five to 10 mm wheel is significant. A red area or flare at the site is also important. Some patients may not show a reaction although their history suggests an allergy. For them, other tests may be needed.
Interdermal testing means a shallow injection of allergen is given. This is an alternative method of skin testing. A RAST test for allergies tests the patient’s blood in the laboratory against certain allergens. This is more expensive and not as sensitive as the skin test. However, it can be useful in a child with widespread eczema when skin tests cannot be performed.
Antihistamines can suppress the skin’s reaction to allergens. Allergists will advise patients at the time they make an appointment how long to remain off antihistamines before being tested.
Other testing methods - Several other testing methods are used by a few doctors, chiropractors, naturopaths, herbalists and others. These include neutralization-provocation, the Rinkel method, VEGA machine, cytochemical analysis, computer analysis, ELISA method and muscle tension measurements while holding a vial of allergen. None of these have been shown to be valid by scientific research.
Environmental control - The first and most effective method of allergy control is removing the allergen. If the cat or dog is causing symptoms, the most effective treatment is to find a new home for the pet. Bedrooms, carpets, drapes and clothes must be thoroughly cleaned. Forced air heating systems in the home should be professionally cleaned. Removing pets is always a difficult decision for the family. However, if the long term effects of keeping the animal are discussed, most people will agree to doing so. Patients who are extremely allergic may suffer serious symptoms when visiting homes with pets. In such cases, treatments with drugs and allergy shots may be necessary. The control of dust mites and moulds has been briefly described above.
Drugs - Antihistamines are a mainstay of the drug treatment of allergies. Newer non-sedating antihistamines taken once a day are the most convenient. For control of seasonal pollen allergy, they should be started before symptoms begin. Many older antihistamines are labeled as non-drowsy. Those products may contain an antihistamine in combination with decongestant and/or analgesic. Some of the other ingredients may be ones the patient should not be using and labels should always be read carefully. Inhaled nasal corticosteroids are safe and can be very effective for the stuffy nose of hay fever. These drugs may be used regularly and daily as prescribed by the doctor. Allergic eye symptoms may require specific anti-allergy eye drops.
Immunotherapy - Use of allergy shots is called immunotherapy. This is a method of boosting the immune system to block the effects of the allergen. It involves injecting increasing amounts of the allergen to achieve control of symptoms. Allergy shots are useful when the other methods do not provide good control of serious symptoms. They are particularly useful with severe cat or pollen allergy. Patients must be motivated to complete this treatment program because it requires regular visits to the doctor’s office for injections. Although they are not common, reactions can occur, so a 30-minute observation period in the clinic is required after each injection.
Adrenaline - Patients who have had severe reactions to a stinging insect or food should carry an adrenaline kit for self-injection or injection by another person.
Allergies can cause a range of problems from brief 'stuffiness' to more severe and prolonged symptoms to sudden, life-threatening reactions. The first step to successful treatment is identifying the cause. Your family doctor can discuss the allergies and their control with you. When your problem warrants a referral, an allergist can assist you and your doctor to identify and respond to specific allergens.
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