Allergies: Causes, Symptoms, and Treatments

What are the most common allergies?

Respiratory allergies affect approximately 1 in 5 Canadians. They occur when the person breathes in certain substances present in the air. The most common allergens are pollen (from trees, grasses, and ragweed); dust mites; mold; allergens of certain animals and insects (dead skin flakes, urine, saliva); and volatile chemical products (smoke, perfume, odours, solvents).

The main symptoms of respiratory allergies are runny nose, nasal congestion, sneezing, watery eyes, and itchy nose, eyes, or roof of the mouth. Respiratory allergens can also trigger or aggravate asthma symptoms by causing shortness of breath or trouble breathing.

Food allergies affect 5% to 6% of young children and 3% to 4% of adults in Canada. These allergies appear soon after a food is ingested, usually within a matter of a few minutes or hours. The severity of the reaction can vary from one allergen to another, one person to another, and even from one reaction to another in the same person.

Although any food can trigger an allergic reaction, nine food groups are responsible for 90% of allergic reactions: eggs, cow's milk, peanuts, fish and seafood (e.g., shrimp, crab, lobster, mussels), soy, nuts (e.g., walnuts, almonds, cashews, hazelnuts), mustard, sesame, and wheat.

Food allergies are allergies that must be taken seriously since they can be fatal if not treated in time. People with a food allergy should have an epinephrine auto-injector on hand at all times.

Drug allergies occur after ingesting or injecting a drug. The drugs most likely to cause allergies are antibiotics, anti-inflammatories, contrast agents used in medical imaging, epilepsy drugs, narcotics, and chemotherapy drugs.

Common symptoms of drug allergies include skin reactions (redness, hives), and in some cases, anaphylaxis. Most of the time, people mistakenly attribute the side effects they experience when taking a drug to an allergy.

If you experience symptoms after taking a medication, consult your pharmacist. They will help you determine the proper course of action. While allergies to medications are rare, they require prompt attention.

Allergies to insect stings, particularly to the venom of bees, wasps, red ants, and hornets, can be serious. They often cause intense itching with swelling at the site of the sting and can cause anaphylaxis and even lead to death. People quickly have trouble breathing, and experience swelling of the face and throat, difficulty swallowing, increased heartrate, dizziness, and a drop in blood pressure.

People with an allergy to insect stings should have an epinephrine auto-injector on hand at all times, ideally two if you are planning an outdoor activity and will be far from the nearest hospital.

Latex allergy, while not as widely known, can be just as serious. Balloons, condoms, rubber household gloves, elastic bands, and some medical devices (gloves, syringes, injectable drug vials) are made using the liquid from rubber trees. Reactions range from skin irritation, known as contact dermatitis, to anaphylaxis.

How long does an allergic reaction last?

Allergy symptoms usually disappear within a few hours to a few days when you are no longer exposed to the allergen. However, some allergens can be more difficult to get rid of. Pollen, as well as dust mite, cockroach, and pet allergens, for example, can remain airborne for a long time in the air and in your home’s ventilation ducts. These allergies tend to be harder to control in the short term.

How do you avoid an allergic reaction?

The best way to avoid experiencing an allergic reaction is to avoid exposure to the allergen that makes you sick. Some allergens can be avoided by taking relatively simple steps, e.g., food, latex, medication, while for others, such as pollen, while you may be able to reduce exposure to the allergen, it is almost impossible to avoid it altogether.

If you have an allergy, be sure to inform all of your healthcare professionals, as in some cases, they will need to take certain measures to prevent you being exposed to the allergen(s).

Can allergies be treated effectively?

Allergy treatments depend on the type of allergen.

Allergies that can cause an anaphylactic reaction, e.g., food or an insect sting, are treated by injecting epinephrine with an auto-injector. Emergency services should always be contacted when epinephrine is administered, as medical supervision is required for several hours due to the risk of a delayed reaction.

For foreseeable allergies that occur on an ad hoc basis, e.g., when visiting a friend who has a cat, an antihistamine is usually recommended and should be taken before exposure to the allergen. A range of prescription and over-the-counter products are available.

For allergens to which you are exposed for long periods. e.g., dust mites or pollens, healthcare professionals usually recommend an intranasal corticosteroid spray or antihistamines, along with measures to reduce exposure to the allergen.

Desensitization or immunotherapy treatments are available to cure—or at least, significantly reduce—certain allergies to animals and pollens.

It can be difficult to find your way around all the treatments available. Don't hesitate to discuss your allergy problem with your doctor or pharmacist. They can tell you which products are appropriate for your allergy, given your overall health. In some provinces, pharmacists are allowed to prescribe medications to relieve allergy symptoms. Be sure to ask for advice. Your pharmacist is there to help!