Allergic Reactions: Symptoms, First Aid Response, and When to Get Help in Canada

An allergic reaction occurs when the immune system responds to a substance that is usually harmless. While the immune system’s role is to defend the body against harmful bacteria and viruses, it can sometimes react aggressively to non-threatening substances known as allergens.

Allergic reactions affect people across Canada and can range from mild discomfort to severe, life-threatening emergencies such as anaphylaxis. Understanding how to recognize and respond to allergic reactions is an important part of general first aid awareness.

What Causes an Allergic Reaction?

The symptoms of an allergic reaction can range from mild to severe. If exposed to an allergen for the first time, the symptoms are usually mild.

Allergies often run in families, meaning individuals with close relatives who have allergies may be at higher risk. While the exact reason allergies develop is not fully understood, certain substances commonly trigger allergic responses.

Common allergens include:

Animal dander
Pollen, mold, or certain plants
Insect stings or bites (such as bees or wasps)
Certain medications (including aspirin or penicillin)
Specific foods such as nuts or shellfish

An individual may be allergic to one or multiple allergens, and reactions may worsen with repeated exposure.

Signs and Symptoms of an Allergic Reaction

The symptoms of an allergic reaction can range from mild to severe. In many cases, the first exposure causes mild symptoms, while later exposures may trigger stronger reactions.

Mild Allergic Reaction Symptoms

Itching
Hives or skin rashes
Scratchy throat
Itchy or watery eyes

Severe Allergic Reaction Symptoms

Abdominal pain, cramping, nausea, or vomiting
Diarrhea
Chest tightness or pain
Difficulty swallowing
Wheezing or shortness of breath
Swelling of the eyes, face, lips, or tongue
Dizziness, weakness, or anxiety
Rapid or irregular heartbeat
Loss of consciousness

Anaphylaxis: A Medical Emergency

A sudden and severe allergic reaction is known as anaphylaxis. This reaction can occur within seconds or minutes of exposure to an allergen and may involve:

Swelling of the airway
Difficulty breathing
A sudden drop in blood pressure

Anaphylaxis is life-threatening and requires immediate emergency medical assistance.

First Aid Response for Allergic Reactions

If the allergen is unknown, or symptoms are worsening, medical care should be sought.

For mild allergic reactions, over-the-counter antihistamines may help manage symptoms.

For severe reactions:

Call emergency services immediately
Check if the person is breathing
Begin CPR if required
Assist with an epinephrine auto-injector if the person carries one
If unconscious, lay the person flat, elevate the legs, and keep them warm

Recognizing these signs and knowing when to act are core topics covered in first aid and CPR training in Canada.

Why Allergy Awareness Matters for Canadians

Food allergies, insect stings, and medication reactions are common across Canada—in homes, workplaces, schools, and public spaces. Because severe allergic reactions can escalate rapidly, early recognition and proper response can be life-saving.

Allergy awareness is frequently discussed in first aid training, alongside airway emergencies and CPR response.

Educational Disclaimer

This information is provided for general educational purposes only and does not replace professional medical advice. Recognition and emergency response to allergic reactions are introduced in certified first aid and CPR training, but medical treatment must be provided by healthcare professionals.