Woman sitting in meadow petting her dog
Woman sitting in meadow petting her dog


Allergens are a part of our lives. But if you know what to look for, you’ll be better prepared to steer clear where you can.

Outdoor Allergens1

Tree Pollen

Trees are the first plants to produce pollen each spring. Depending on where you live, tree pollen season can start in late winter or early spring.2

Leaf Mould

In the fall, piles of rotting leaves provide ideal conditions for mould to thrive. Leaf mould goes dormant in the winter but resumes growing as soon as the weather gets warmer.3

Grass Pollen

Grass pollen is released from late spring through early summer and, because grasses are so widely grown, they’re responsible for a lot of nasal allergy symptoms.

Indoor Allergens

Black Mould

Extreme humidity, flooding, or other types of water damage spur black mould growth. It tends to grow on building materials like fiberboard and on paper, dust, and lint.4,5

Dust Mites

It’s actually the waste products of dust mites (microscopic bugs that feed on the tiny flakes of human skin) that circulate as part of household dust and trigger allergic reactions.6


Cat and dog dander (microscopic bits of skin and saliva) is the most problematic among pet-related allergy triggers.

1 Allergies. Indoor vs. Outdoor. Flonase. Available at https://www.flonase.com/allergies/indoor-vs-outdoor-allergens/ (accessed 10 July 2018)

2 Naclerio, R. M. et. al. 2010. Pathophysiology of nasal congestion. International Journal of General Medicine. Dovepress

3 Eccles, R. 2005. Understanding the symptoms of the common cold and influenza. The Lancet, Vol. 5

4 Naclerio, R. M. et. al. 2007. Observations on the ability of the nose to warm and humidify inspired air. Department of Surgery, Section of Otolaryngology-Head and Neck Surgery, The University of Chicago, Chicago, IL, USA

5 Centers for Disease Control and Prevention. Facts about Stachybotrys chartarum and Other Molds. Available from https://www.cdc.gov/mold/stachy.htm (accessed 10 July 2018)

6 Eccles, R. et. al. 2008. The nasal decongestant effect of xylometazoline in the common cold. American Journal of Rhinology, Vol. 22, No. 5