Return to Previous Page

Pollen, Pollen Everywhere!

by David Shulan, MD, FAAAAI

Allergy image

For people with seasonal allergies, pollen levels can be a useful tool. Yet many don’t fully understand what they are and how monitoring pollen levels can help to reduce their symptoms.

What is pollen?
Pollen – the tiny, male cells of flowering plants – can cause itchy or watery eyes; a stuffy, runny nose; allergic eczema; and asthma. The pollens that cause the most problems are those that are spread by wind, such as those from trees, grasses, and weeds. These very light pollens can blow hundreds of miles from their origin. As a result, you can experience symptoms caused by pollens that were released hundreds of miles away.

Pollen levels often include these problematic pollens, some of which are from species not found in the local area. Contrary to what many people believe, plants with large flowers usually do not cause major allergy symptoms, as they have heavy pollens that drop out of the air quickly.

What do pollen levels measure?
Pollen levels measure airborne allergens. For sensitive individuals, monitoring pollen levels can help limit outdoor exposure at peak pollen times and in turn, reduce their allergy symptoms.

Contrary to what many people believe, plants with large flowers usually do not cause major allergy symptoms, as they have heavy pollens that drop out of the air quickly.

Various concentration levels are associated with the amount of pollen recorded. In general, absent means no measurable pollen is recorded. Low means that only very sensitive individuals will experience symptoms. Moderate means that many more individuals will have symptoms. High means that most sensitive individuals will experience some symptoms. Very high indicates that all sensitive individuals will have symptoms and most will have more severe symptoms.

What affects pollen levels?
Location is one of several factors that can influence pollen levels. A ragweed count of 100 grains/cubic meter would be considered very high in Albany, NY, but only counts in the thousands will raise eyebrows in Iowa City, IA, where they can reach 5,000. Generally, the number of ragweed plants in the Midwest is much higher than in the eastern United States, but ragweed in smaller numbers can be found pollinating in Florida during the spring.

Weather conditions also play a role in pollen levels. Moderate temperatures with low humidity and a gentle breeze keep pollen in the air, whereas rain washes the pollen out. A windless day will result in low levels since pollen needs wind to disperse. High levels of humidity will make the pollen grains heavier, meaning they will drop out of the air more quickly.

Can allergy symptoms vary throughout the season?
Throughout the season, individuals can vary in their level of sensitivity. Many become more sensitive as the season progresses. This process, called allergic priming, means that you may not have problems with low pollen levels at the beginning of the season, but toward the end of the season, low levels may start to cause symptoms.

Who calculates and reports pollen levels?
The National Allergy Bureau is the section of the American Academy of Allergy, Asthma & Immunology’s Aeroallergen Network responsible for reporting current pollen and mold spore levels to the public. The NAB provides the most accurate and reliable pollen and mold levels from approximately 78 counting stations throughout the United States, as well as several counting stations in Canada and Argentina. To view the pollen levels for your area, visit


Dr. David Shulan is an allergist/immunologist based in the Albany, NY, area for nearly 24 years. He’s currently in practice at Certified Allergy and Asthma Consultants and is the director of its NAB-certified pollen counting station.

Source: American Academy of Allergy, Asthma & Immunology,

This article was originally published in Coping® with Allergies & Asthma magazine, March/April 2010.