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Demystifying allergies

Published on October 21, 2018 at 14:41 / Updated on February 2, 2023 at 20:56

The immune system is our body’s defence mechanism against assaults from the outside. It sometimes misidentifies its enemies and perceives a harmless agent as an assailant. Our body then reacts in an excessive manner and activates a defence mechanism that can be more or less significant and can manifest in various ways. This is what we call an allergic reaction.

For this phenomenon to occur, there must be initial contact between our body and the sensitizer (another word for allergen). This is the sensitization phase, during which the body produces an immune response specific to that allergen.

Afterwards, each time the body is once again exposed to the allergen, the allergic reaction cascade will be activated. The body will release a chemical substance called histamine – the main culprit in the unpleasant manifestations of allergy.

There are many types of allergic reactions. In fact, everyone has a different sensitivity to allergens and reacts in a unique way when coming into contact with them. Allergies truly have a thousand faces.


Some allergens are more likely to induce a hypersensitivity reaction than others. While there are a great number of allergens out there, a few specific families of them are at the root of most known allergies:

Airborne allergens

They are present in indoor or outdoor air and they include mites, pollen, mould and animal dander.

Food allergens

They are substances that can be found in food. Allergic reactions can occur with any food (or one of its components), but some are more common than others, such as allergies to milk (cow’s milk specifically), eggs, soy, wheat, shellfish, fruit, peanuts and nuts.

“Contact” allergens

They are mainly found in the various chemicals we encounter, such as perfume, latex, cosmetics, metals and vegetable extracts.

“Venom” allergens

They are responsible for allergies to the sting of insects such as bees, wasps, hornets and even ants. This type of reaction mustn’t be underestimated, as it can induce particularly severe reactions.

Drugs allergies

They are becoming increasingly common and are a major concern for pharmacists. It usually manifests as a full-body rash, but may also cause edema (swelling), which could have serious consequences. Drug allergies can be attributed to the molecule itself, to one of the products created when digesting the product, or to one of the inactive ingredients (colorants, preservatives, etc.).

The most common allergy manifestations

Allergies can manifest through a great variety of signs and symptoms. Some are more specific and easy to recognize, whereas others are less common and particularly difficult to identify. Each allergen has its own reaction, and everyone has a specific reaction to the allergen.

An allergic reaction can therefore range from mild to very severe based on allergy type, degree of exposure and individual reaction. Thankfully, most reactions are not serious, although they can cause much discomfort.

Allergic individuals usually present with several tell-tale symptoms that point to a given type of allergen. For example, in the presence of a runny nose, itching, sneezing or tearing, we can suspect an airborne allergen. Skin reactions, on the other hand, can be the result of a food, drug or chemical allergy. Moreover, a food-based problem can manifest through a digestive disturbance such as nausea, diarrhea or severe abdominal pain.

Allergic reactions to be more serious

They are relatively rare for allergic reactions to be more serious. The most dangerous is anaphylactic shock, which is triggered by food allergies in nearly 50 percent of cases. Drug allergies, for their part, account for 15 to 20 percent of anaphylactic shock cases, while venom allergens (wasps, hornets and other insects) are the third-leading cause.

Anaphylactic shock 

It occurs quickly and violently following contact with the allergen. It causes a marked increase in heart rate, which may be accompanied by significant edema of the throat, making it difficult to breathe. In some cases, there may also be a generalized skin rash, abdominal pain and diarrhea.

Anaphylactic shock is a medical emergency and requires immediate medical help, as it could be fatal. Individuals prone to this type of reaction must remain vigilant and take all necessary precautions in order to avoid coming into contact with the allergen in question.

Diagnosis and clues

Do you always get your itchy eyes and congestion in the springtime, or is it rather whenever you visit a friend who has a cat? Have you noticed that your rash occurs whenever you eat a specific food? This is the type of clue that will help an allergist perform an investigation and identify which allergen is making your life so miserable.

To confirm their suspicions, allergists perform a skin test. The idea behind the test is simple: 

  1. A small dose of pure allergen is placed on the skin. 
  2. Next, a small pinprick is made through the drop in order to create a small opening in the skin, which allows the allergen to come into contact with the immune system. 

Normally, there should be no reaction. In allergic individuals, however, the contact will activate the allergic reaction cascade and a small, red pimple-like papule will appear. This quick test can be analyzed in 10 to 20 minutes, causes little or no pain, and the marks made by the reaction soon disappear.


There are various ways to control the unpleasant symptoms of an allergy. The most effective way to do so is to completely avoid all contact with the allergen, especially in the case of a food or contact allergy. Unfortunately, that’s sometimes impossible, so other measures are then necessary.

While they may be unpleasant, the symptoms for most allergies are minor and isolated. In such cases, you can use over-the-counter medication whenever you experience the manifestations of an allergy. There are many different agents that are effective at controlling allergy symptoms. Most are antihistamines, in other words agents that act on the production of histamine in order to block the allergic reaction. They all have their advantages, disadvantages, adverse effects and contraindications.

Pharmacists can help you choose among the various products available, taking into consideration the type, frequency and intensity of your symptoms. Pharmacists can also refer you to a physician when necessary.

Other treatments are available for more troublesome or dangerous allergies. For airborne allergens such as pollen, animal dander or mites, immunotherapy can reduce the body’s reaction when faced with an allergen. This technique involves getting the immune system to respond differently to an allergen by following a complete desensitization protocol.

Lastly, there are adrenaline injection devices for the emergency treatment of anaphylactic shock (Epipen® and Twinject®, which contains two adrenaline doses). Individuals who have previously had a severe allergic reaction or anaphylactic shock should always carry one of these products on them. Adrenaline helps clear the respiratory tract and temporarily delays the progression of symptoms. This can save the life of the person in distress by buying a few additional minutes to get emergency medical help.

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