About one-quarter of Canadians suffer from seasonal allergies, according to the Canadian Society of Allergy and Clinical Immunology (CSACI). Common symptoms of seasonal allergies include sneezing, an itchy nose and throat, nasal congestion, a runny nose, coughing and watery, itchy, and reddened eyes.

A common cold is usually associated with a variety of symptoms in addition to a runny nose: cough, body aches, fatigue, and occasional yellow nasal discharge. All of these symptoms usually resolve in one to two weeks.

https://globalnews.ca/news/10333131/spring-allergy-season-canada-2024/#:~:text=About%20one%2Dquarter%20of%20Canadians,%2C%20itchy%2C%20and%20reddened%20eyes.
https://www.dukehealth.org/blog/common-allergy-questions-and-answers

The immune system protects your body against foreign substances by starting a response. This immune response releases antibodies. The antibodies protect you against the threat. Sometimes the immune system attacks a substance that should be harmless, like food or pollen, and this causes allergies.

https://www.urmc.rochester.edu/

While the timing and severity of an allergy season vary across the country, the following climate factors also can influence how bad your symptoms might be:

Tree, grass and ragweed pollens thrive during cool nights and warm days. Molds grow quickly in heat and high humidity. Pollen levels tend to peak in the morning hours. Rain washes pollen away, but pollen counts can soar after rainfall. On a day with no wind, airborne allergens are grounded. When the day is windy and warm, pollen counts surge.

https://acaai.org/allergies/allergic-conditions/seasonal-allergies/

Common allergic reactions, such as hay fever, certain types of asthma, and hives are linked to an antibody produced by the body called immunoglobulin E (IgE). Each IgE antibody can be very specific, reacting against certain pollens and other allergens. In other words, a person can be allergic to one type of pollen, but not another.

https://www.hopkinsmedicine.org/health/conditions-and-diseases/allergies-and-the-immune-system

​https://sciencenotes.org/types-of-antibodies-and-their-functions/

Even kids who have never had seasonal allergies in years past can develop them. Seasonal allergies can start at almost any age, though they usually do not develop before a child is 2 years old. Most people with seasonal allergies develop them by age 20.

https://kidshealth.org/en/parents/seasonal-allergies.html#:~:text=Even%20kids%20who%20have%20never,develop%20them%20by%20age%2020