Allergens

An allergen is a molecule that in some people, can trigger the immune system into producing an allergic reaction¹.

Food allergens

While any food item could be responsible for an allergy, the most commonly allergy causing foods include: milk, egg, fish, shellfish, tree nuts, peanuts, wheat and soy².

Inadvertent or accidental exposure can occur with food allergens because they may be present in trace amounts due to contamination during the manufacturing process.

Milk

A milk allergy causes a person’s immune system to overreact to milk proteins. People with an allergy to cow’s milk may also be allergic to milk from other animals, including sheep and goats³. There are two main types of milk protein: casein and whey. Milk proteins are found in many foods, including all dairy products. Other foods such as sausage, meats and other nondairy products may contain casein. Milk protein has also been found in some chewing gum³.

Egg

Egg allergy develops when the body’s immune system becomes sensitised and overreacts to proteins in egg whites and/or yolks. People with an allergy to chicken eggs may also be allergic to other types of eggs, such as goose, duck, turkey or quail; an allergic reaction can occur by eating or even touching an egg⁴.

Fish

Contrary to other food allergies, which usually first appear in babies and young children, fish allergy can appear in adulthood³. People with allergy to finned fish are not necessarily allergic to shellfish. A variety of prepared foods contain food under some form (sauces, stock, etc.) and should be avoided by people with fish allergy⁵.

Shellfish

Shellfish allergies are more frequent in adults but can also affect children. Crustacean shellfish (shrimp, lobster and crab) cause the greatest number of allergic reactions⁶. Shellfish can be found in a variety of sauces and prepared food and even trace amounts can cause an allergic reaction.

Tree nuts

Tree nut allergies are usually a life-long condition⁷. Tree nuts include almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios, and walnuts. Tree nuts can be found in many foods: baked goods, alcohol, herbal teas, snacks, spreads, etc. Tree nuts can also be found in non-food sources such as massage oils, shampoo, cosmetics, etc⁷. Foods that don’t contain tree nuts can also be contaminated during manufacturing processes.

Peanut

Peanuts are part of the legume family. Peanut is present in a large variety of foods (baked goods, cereal, salad dressing, candies, meat substitutes, etc.) as well as in non-food sources (cosmetics, sunscreen, pet food, medications, etc.). Peanut odours and inhaled peanut protein particles may also cause allergic reactions⁸. Foods that don’t contain peanut can also be contaminated during manufacturing processes.

Wheat

Wheat allergy most commonly develops in infants and tends to be outgrown. Adults who develop a wheat allergy are likely to retain the condition. Wheat is found in many foods such as pasta, bread, sauces, desserts as well as in non-food sources (cosmetics, bath products, vitamins, etc.). A gluten intolerance is not an allergy⁹.

Soy

Soy allergy generally develops in infants and children under three. Soy, which is part of the legume family, is a common ingredient in baby formulas and processed foods (broths, tinned tuna, soups, mayonnaise, etc.). Allergic reactions to soy can affect the skin, respiratory tract, gastrointestinal tract and/or cardiovascular system¹⁰.

Respiratory allergens

Respiratory allergy can be seasonal or occur year-round. The main respiratory allergens include:

Pollen

Pollens are suspended in the air on sunny and warm days, they can be carried by the wind over several miles. The amount of pollen in the atmosphere is lower on rainy days as well as on cold and humid days. Pollens responsible for respiratory allergies come from three categories:

• Grasses. The Poaceae (grass) family includes more than 12,000 different species. Grasses are found in gardens, lawns, forests as well as on water or on rocks. Even a tiny concentration of grass pollen is enough to trigger an allergic reaction. Fodder and cereal grasses which can trigger allergies include: dactylic (cocksfoot or orchard grass), timothy, sweet vernal, ryegrass and bluegrass. In the Northern hemisphere their pollination period extends from March to September with peaks in May, June and July.
• Trees. Tree pollen which can trigger allergies include: the Betulaceae family (birch), the Fagaceum family (beech, oak), the Oleacceae family (ash, olive tree), the Cupressaceae family (cypress, juniper, cedar). Their pollination period is spread over several months (from March to September in the Northern hemisphere) and varies from one species to another.
• Weeds. Species from the herbaceous family have soft and supple stems. Their pollens, which are small and light, can remain suspended in the atmosphere for a long period of time and can be carried over long distances. Herbaceous weeds which can trigger an allergic reaction include: mugwort, nettle, lamb’s quarters, ragweed, sage, Russian thistle… Aromatic plants such as lemongrass, tarragon, and wormwood are part of the same family (Asteraceae). Their pollination season in the Northern hemisphere goes from March to September with peaks in July, August and September.

House dust mites

House dust mites, which are part of the spider family, measure between 0.2-0.4mm and are present in all households where they tend to be more numerous in bedding, upholstery, carpets, etc. House dust mites are one of the major causes of allergic rhinitis with symptoms such as congestion, sneezing, a dry cough or bronchitis which can lead to asthma. House dust mite allergies are perennial.

Mould

Fungi can be found both outdoors (fallen leaves, compost, grasses, etc.) and indoors in damp areas (bathroom, kitchen, etc.). The spores released by the fungi can be carried by wind and dew. The microscopic size of fungi spores, which ranges from 3 to 10µm), enables them to easily penetrate the respiratory tract.

Mould can trigger respiratory allergies, both on a seasonal and perennial basis, such as allergic rhinitis, conjunctivitis and asthma.

Pets

Allergies to cats are the most common type of allergy to dander. And represent two thirds of allergies to pets. Contrary to common belief, what triggers an allergic isn’t pet hair but a substance (Fel d 1) found on the pet’s fur. The allergen can be found throughout homes, in bedding, upholstery, rugs and is suspended in the air.

Sensitization to dogs is less common than cat allergies. As with cats, the allergenic protein (Can f 1) is present on dog fur but is less allergenic.

Other pets can also trigger allergic reactions: rodents (guinea pigs, hamsters, mice, rats and rabbits), exotic pets (chinchilla, reptiles, arachnids, amphibians), birds (parrots, canaries, parakeets), farm animals (cows, horses, goats, sheep).

Venom

Venom from stings and bites can occasionally cause life threatening reactions though in most people, they will only cause a local reaction at the site of injury¹¹.