I am looking for a dataset containing allergy rates or pollen counts for cities/counties/census tracts. Ideally, the dataset would include rates of specific kinds of allergies, or for pollen counts, track the counts by species that are known to cause seasonal allergies.
In the United States, the National Allergy Bureau is the primary source of pollen measurements. Their network is comprised of approximately 80 monitoring stations which collect 24-hour samples of ambient pollen concentrations using either Burkard or Rotorod samplers. Simplified categories are presented on their website (e.g., "Weeds- Low Concentration"). Researchers can submit requests for the raw data (concentrations of various pollen types, generally identified to the genus level), but the data request process takes several months.
Some data on allergies is available through the National Health Interview Survey, which can be aggregated to the state level. I haven't heard of any national-scale datasets that have allergen sensitization rates at finer spatial resolutions than that.