Yes, allergy symptoms related to pollens and certain outdoor molds can change from one year to another. In large part, changes in the concentrations of allergens in the air underlie variation in symptoms. Allergen concentrations are very dependent on climatic conditions. Varying weather patterns can cause differences in the levels of pollen allergen in the air from one year to another. The same holds true for outdoor molds.
Pollen levels depend on how much pollen is produced by and released from plants, and dispersal (e.g. by wind). The amount of pollen produced depends on the duration of the growing season, and the size of the territory in which plants can grow. Rising global temperatures may contribute to longer growing seasons and increased total levels of pollen over a season. However, increased urbanization means less land on which plants can grow, which could decrease levels of pollen in urban areas. The release of pollen from plants is affected by the time of day, temperature, and humidity. Dispersal of the pollen depends on temperature, humidity, wind speed, and air turbulence. How all these factors interact determines the pollen count in the air, and it is a very complex interaction.
Some consistent patterns have been noted in this regard: certain pollen counts, such as for ragweed, are lowest around sunrise and highest at mid-day, after the pollens have been dried of dew and become wind-borne. Heavy rainfall is usually associated with lower pollen counts. However, in some instances, rain can contribute to pollen release. Pollen and mold spore release can also be affected by electrical charge in the air, which can vary if there has been thunderstorm activity.
Overall, one expects that when pollen counts or mold concentrations are higher, allergy sufferers will experience more severe symptoms compared to seasons where those counts are lower. Higher allergen concentrations might also trigger symptoms, whether mild or severe, in a larger number of individuals.
Aside from climatic effects on airborne allergens, more local environmental influences such as the level of indoor humidity can affect indoor concentrations of allergens such as dust mites and molds (usually different than the kinds of molds found outdoors). The higher the humidity, the more dust mites and molds there will be, which would be expected to increase the symptoms experienced by allergy sufferers.
These would be the main players in the variability patients may notice in their allergy symptoms from one year to another. Another contributor to variability relates to whether or not patients are taking any treatments, and how well they are following their treatment plans. Patients who are taking long-term immunotherapy injections (also called desensitization) may expect to have improving symptoms over the years they are receiving treatment, and for some time afterwards. Finally, the immune system’s response to environmental allergens can also change over time, although the way in which it does so is difficult to understand, and there is no consistent pattern for all individuals. However, this can also account for changing symptoms from one year to another.
The views expressed are solely those of the author based on his knowledge and expertise and do not necessarily represent the views of the manufacturer.
If you think you are experiencing allergy symptoms, please consult your healthcare professional for a definitive diagnosis.