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The Clinical Utility of Pollen Counts

Authors: Dr. Carmi Geller-Berstein, Zabludovicz Center for Autoimmune Diseases, Sheba Medical Center and Dr. Jay Portnoy, Division of Allergy, Asthma and Immunology, Children's Mercy Hospital


In this review, we describe how pollen counts are performed, the health effects caused by exposure to varying amounts of pollen, the clinical utility of reporting pollen counts to the public, and how that information can be used by patients who have allergies to improve their health.

The public is very interested in pollen counts, particularly if the counts provide a forecast of expected pollen exposure for the next few days. Traditional pollen counts are labor-intensive; poorly distributed; and, since the counts are usually 1-day-old, do not provide forecasts that can be acted on. New methods that provide short- and long-term pollen forecasts can provide this information to allergic individuals so that they can respond to changing outdoor conditions.

Studies of the relationship between artificial and natural exposure to pollen and development of symptoms have provided improved understanding into how much pollen it takes to cause symptoms. Thresholds for pollen counts that trigger symptoms vary by pollen type, sensitivity of the population, and interactions with other atmospheric exposures. Strategies to inform the public when the pollen count poses a health risk have been proposed along with computerized systems that provide personalized pollen alerts. The best performing public notification system was a "traffic light system" that reported pollen exposure as low, 0-30; intermediate, 31-50; or high, 51-150. This system outperformed other threshold systems used in Sweden and in Britain/Denmark. Continued improvements in pollen forecasting models combined with data provided by automated pollen counters and better public reporting should permit allergic individuals and urban planners to adapt effectively to changes in outdoor aeroallergen exposures.


Allergic rhinitis (AR) is estimated to affect approximately 1030% of the worlds population. In 2012, 7.5% or 17.6 million adults and 9% or 6.6 million children were diagnosed with AR in the USA. It is associated with substantial reduction in the quality of life primarily due to impaired sleep which can lead to fatigue, irritability, and even absence from work and school. This is particularly problematic during peak pollen seasons. Direct costs include 11.1 million medical visits in addition to numerous days missed from work and school [5]. AR also is associated with indirect costs due to presentism w hich occurs whe n one is p resent at work or school but not performing well due to fatigue.

Approximately 7.6% or 18.4 million adults and 8.4% or 6.2 million children in the USA are affected by asthma. In 2014, there were 20 million ED visits for asthma and 3651 deaths due to asthma for a death rate of 1.1 per 100,000 population. While medical management of AR and asthma is usually effective, the treatment itself has a burden including its cost, adverse effects, and the need to obtain and take medications. Allergen immunotherapy, while highly effective, is also associated with expense and burden when done effectively.

Environmental control has been proposed as an approach to reduce the morbidity due to AR and asthma. This primarily has been limited to control of the indoor environment because it can be more easily manipulated than outdoor exposures, though outdoor aeroallergens can penetrate indoors if windows and doors are open. While exposure to outdoor pollen, fungi, air pollution, and particulates cannot easily be modified by an allergic individual, one can avoid going outdoors when exposure is likely to be high and to live in locations where exposure is relatively low. To do this, it is necessary to measure and predict exposure to outdoor aeroallergens and to understand how it affects an individuals health.

In this review, we will examine how pollen counts are obtained and whether there is c linical utility in reporting counts to the public. Since there is likely to be a dose-response between exposure to pollen and AR and asthma morbidity, we will review evidence for that relationship and how pollen information can best be used by the public to ameliorate symptoms. Finally, we will describe long-term changes in pollen exposure and how that information can be used for urban planning.


Read the full white paper via Clinical Reviews in Allergy & Immunology.

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