This cold spring brought a late season for the trees but this does not have any impact on what is going to happen in August and the fall for outdoor pollen and mold spores. There are many weeds that cause seasonal allergies. Some of them include plantain, nettles, ragweed and others. But only weeds that are mostly or partially air pollinated are included in outdoor air samples. The weeds do not include ones that have a strong smell, colourful flowers or do not get airborne (Dandelion). These other weeds can cause allergic reactions but only on contact with the skin.
Ragweed is the most well known and potent of the weed allergens in the summer and fall. This year it has shown up early at many of our sites already. This is due to some of the cooler weather we have been having, as part of our summer months. Ragweed does not generally like higher temperatures in the 30 degrees or higher. Nor does it like cooler temperature, less than 24 degrees Celsius, which have been occurring for a few days in a row this summer. So, typically the main season with the higher counts for ragweed starts early to mid- August.
Ragweed is found in some of our Maritime collecting sites but generally not in high numbers. The places where ragweed is found in high numbers are in the Provinces of Quebec, Ontario and Manitoba. The locations we have in the Province of Saskatchewan have low counts except for Regina. Regina has a significant season compared to Saskatoon and Prince Albert. The Provinces of Alberta and British Columbia have no ragweed or very little pollen is observed at our locations.
The main ragweed season in August and how high the counts are is dependent on how high the temperatures are and how much rain we get. A very hot and dry August will delay the moderate and high counts and the season will be lower. Ragweed Allergy sufferers can be subjected to low counts for almost a month which means there immune system is being primed to the antigen for a long period of time. The counts start going lower around the second week of September and will last with low counts until a hard frost.
The other outdoor allergens that are significant and play an important role are the fungal spores. These allergens are generally poorly understood and are often neglected as the possible cause of a person’s allergic reactions. Fungal spores like Cladosporium, Alternaria and others are common and in abundance come June and July and until October.
Another group of fungal spores are the Basidiomycota. They are a group that is not recognized by many Allergists and allergy sufferers as a possible cause of allergic reactions. This group of fungi are abundant in nature and many are observed on our samples. Ganoderma, a fungus found on decaying trees, and Coprinus, which is a mushroom common on lawns, are very common in outdoor air at this time of the year and are often the cause of seasonal allergies.
There are many other of these fungal spores and too many to mention. Ragweed is such a prevalent allergen and so well known that there is an oversight of the importance of these types of potential allergen which occur in high numbers along with the ragweed season or even after ragweed is in low numbers. Out west, where there is no ragweed, the fungal spores are forgotten as a potential source of seasonal allergies. With more information being presented perhaps these fungal spores will be considered more when patients present with allergies.
Written by Frances Coates from Aerobiology