For many people, seasonal allergies are more than just an annoyance—they can be debilitating.

Hay fever, also known as allergic rhinitis, affects nearly one quarter of Americans each year and is one of the top five chronic diseases in U.S. adults. Nearly three in four people will have an allergic reaction to some type of outdoor allergen such as tree, grass, or weed pollen at some point in their lives.

The societal costs of all that sneezing, coughing, and watery eyes is extreme—seasonal allergies are responsible for nearly four million missed work days annually. Each year, hay fever costs the U.S. more than $8 billion in lost productivity, medications, and doctor's visits.

Pollen Counts

For those suffering with seasonal allergies, pollen counts can be invaluable.

An allergy index measures how much pollen is in the air in a particular area at any given time. Government agencies, allergists, and educational institutions, as well as private physicians and commercial research companies, have worked together to set up systems to measure pollen for a variety of different private and public applications.

For instance, a pharmaceutical company may use the information to research and develop new medications while a government agency may use it to warn allergy sufferers about daily risks.

A pollen count is expressed in "grains of pollen per cubic meter over a 24-hour period." Counts range from 0 (very low) to 12 (very high). Around 2.5, allergy sufferers will begin noticing mild symptoms such as watery eyes and sneezing. At 9.7, allergy sufferers will begin experiencing severe reactions.

Pollen samples are taken using air-sampling devices that are often placed on rooftops several stories above ground level. Pollen grains are captured on a sticky surface and then examined under a microscope where they are identified and counted. Because most of these types of allergens travel on the wind, a single count is relevant for large geographical areas.

Pollen Forecasting

Another piece in developing an allergy index is pollen forecasting.

Much like a weather forecast, a pollen forecast uses weather information from an agency such as the National Oceanic and Atmospheric Administration (NOAA) to predict what pollen levels will be in the future.

It can be useful information for allergy sufferers in planning their days and in deciding whether or not to take medications. Along with weather information such as temperature and precipitation forecasts, historical pollen counts are used in pollen forecasting as well. In many places, forecasts are available on local television and radio broadcasts as well as in newspapers. National forecasts can be found online at the American Academy of Allergy, Asthma and Immunology's National Allergy Bureau website at or at

Take Action

Of course, to be useful to allergy sufferers, an allergy index must spur them to action. People who are concerned about pollen can take the following steps to minimize their exposure:

  • Tree pollens are active during the spring and peak between 10 a.m. and 5 p.m. each day. Grass pollens (summer) and ragweed pollens (fall) are most active in the morning between 5 and 10 a.m. A person should limit her exposure during these times, especially when pollen counts are high
  • Pollen counts are usually low on cloudy days and lowest following a rain.
  • When coming in from outside, remove and launder clothing.
  • Shower when coming in from outside, especially when pollen counts are high.
  • Keep windows and doors shut, and run the air conditioner.
  • Vacuum often using a cleaner with a high-efficiency particulate air (HEPA) filter. People with serious allergies should delegate this task.