Allergen Update
London, Ontario
Predominant pollen:
The tree pollen seasons can fluctuate from year to year by as much as two to four weeks at this site. The pollen seasons described here try to cover the time when each can occur.
Acer sp.- The main maple season can occur from early April to mid-May with moderate to high counts observed. There is also a season with moderate and high counts which can occur from the latter part of March to early April. Certain species are known to cause allergic reactions.
Alnus sp.- Alder season occurs from mid-March to the end of May with fluctuations in the counts from low to high due to the number of species present. The season is highly effected by the weather and significant counts can be observed for about a week during the month of April and again late May to early June.
Betula sp.- The birch season, with significant counts, can occur from mid-April to early June with counts ranging from low to high. The season is very sporadic from year to year which is due to the number of species present and the effect of weather. Birch look-a-likes' season lasts one to two weeks and can occur from mid-April to about mid-May and the counts are mostly in the low to moderate range.
Populus sp.- The poplars and aspens have two distinct seasons with the first one, which lasts about one week, occuring between mid-Marh to early April. The main season is longer, some years lasting almost a month, it can occur during the month of April and last into May. Some of the counts are high and may cause allergic reactions.
Cupressaceae group- The cedars, junipers, and yews produce low to high counts and the season varies a great deal from year to year. The season can occur from March throughout April.
Fraxinus sp.- The ash pollen season lasts approximately four weeks and can occur from early April to early June. Some low to high counts are observed and they are considered to be allergenic only in highly sensitized individuals.
Pinaceae group- This includes the spruce, fir and pine trees. Some high counts are observed and the season can vary by as much as a month. The season can start from early May to early June and can end early to late June.
Quercus sp.- The oaks have two distinct flowering periods which is due to the different species present. The seasons are both effected by weather conditions. The first season, which lasts approximately one week, can have low to high counts and occurs during the month of April. The second season, which lasts at least a month, can occur from late April through to early June. Some of the species are considered highly allergenic.
Salix sp.- Pollination lasts about four weeks and can occur from mid-April to mid-May with moderate counts observed.
Carya sp.- The hickories have a short season lasting approximately three weeks, moderate and high counts are observed. The season can occur between early May and until early June.
(Castenea- The chestnuts are important allergens and the season lasts approximately two weeks and it can occur from mid-May to mid-June. The Horse Chestnut, which is the most allergenic, is found in low to moderate numbers for approximately one week.)
Juglans sp.- The walnuts are considered important in causing allergic reactions. The pollen season can start from early May to mid-May and can end late May to mid-June. Low to high counts are observed at this site.
Ulmus sp.- The elms are considered important allergens. There are two distinct seasons, each lasting about two weeks, the first can occur early to late March and the second early to late April. Some high counts are observed but the seasons can vary since elms are highly affected by weather.
Morus sp.- The mulberries produce very high counts at this site. The pollen season lasts approximately four to five weeks and can occur from early May to mid-June. Could be a siginificant allergen for those individuals who are sensitized.
Gramineae- The grass season is from late April to October. Moderate to high counts are observed from the mid-May to mid-July.
Ambrosia sp.- Ragweed pollen is observed from early July to late October. Very high counts are obtained from the second week of August to early October.
Urtica sp.- Nettles pollinate from late May to late September and moderate counts are observed from mid-July and into August. This may cause allergic reaction in highly sensitized individuals.
Plantago sp.- The plantains pollinate from June to early October. The counts are generally in the low range and occasionally moderate. This may cause allergic reaction in highly sensitized individuals.
Predominant spores:
Diatrypaceae sp.- The counts are sporadic throughout the whole counting season. High counts can be observed from March to well into October.
Leptosphaeria sp. & Leptosphaeria look-a-likes- These two are grouped together since they are in the same class of fungi and are similar microscopically. The season is May to early October with fluctuations in counts from day to day which is probably due to the effect of weather. Highest counts are observed from June to the end of September.
Erysephe (Oospora)- Powdery mildew - The season is from May to mid-October. Mostly moderate counts are observed.
Boletus sp.- The counts for this spore do get high and may be significant in causing allergic reactions. The season is July to mid-October.
Coprinus sp.- This mushroom can produce some very high counts from May to late October. It is considered an important allergen.
Ganoderma sp.- The bracket fungus can produce very high counts from July to mid-October. During the months of May and June the counts are moderate to high. It is considered an important allergen.
Uredinales- The rusts do not occur in really high numbers and allergenic properties are not well understood. The season is from June to late October.
Ustilaginales- The smuts can reach high counts, allergenicity is unknown. The season is May to mid-October. Very high counts are observed in September and October.
Alternaria sp.- Some high counts are observed and certain species are known to cause allergic reactions. The season is from May to the end of September.
Penicillium & Aspergillus sp.- These spores are found throughout the whole counting season and are probably present in significant numbers beyond that. The highest counts are observed from July to well into October.
Cladosporium sp.- The most abundant spore found throughout the whole season. This spore exists all year round but very high counts are known to occur from May to late October.
Epicoccum sp.- Some species are known to cause allergic reactions. The season is from June to mid-October with some high counts.
Fusarium sp.- Counts are very sporadic from June to mid-October. Majority of highest counts are observed in late summer and fall.
Helicomyces sp.- Season is from May to the end of September producing moderate and very high counts. The season is very sporadic.
Torula sp.- Moderate counts are observed in September and October.
Polythrincium sp.- Moderate counts are observed mid-August to the end of September.
Pithomyces sp.- Moderate counts are observed late July to early October.
Myxomycetes- Moderate counts are observed from June to late September.
Last Updated: 3-March-2006
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