Pollen Index

Today's pollen and allergy information. Please specify a U.S. location.

Pollen and Allergies

As a ritual, each spring summer and fall, tiny particles known as pollen are released from trees, grasses and weeds. Pollen is transported by air currents and enters human noses and throats, triggering an allergic reaction named allergic rhinitis, also known as Pollen Allergy. According to the National Institute of Allergies and Infectious Diseases, a branch of the National Institute of Health, approximately 35 million Americans complain from upper respiratory symptoms related to pollen.

Not everybody is allergic to pollen. Scientists believe that some people inherit a tendency to be allergic and respond with a specific immunological reaction. In an allergic reaction, the body's immune system generates a type of antibody called immunoglobulin IgE. The antibody developed is specific for each type of pollen. ie: ragweed, oak, sagebrush, etc. Each plant has a pollenation period that is more or less the same from year to year. The length of the pollenation period is dependent on the relative length of night and day, and the geographical location. More pollen grows in the northern latitudes of North America in this time period.

Pollen count is a measure of how much pollen is in the air in a certain area at a specific time. It is expressed in grains of pollen per square meter of air collected over 24 hours. Pollen counts tend to be highest early in the morning on warm, breezy days and lowest during chilly, wet periods. Weather conditions during pollenation can effect the amount of pollen produced and its distribution.

Thunderstorms can precipitate respiratory difficulties. Initially, windy conditions that usually precede storms stir dust, mold, pollen and this may activate allergies. Later on, heavy rains tend to break pollen into small particles, allowing the smaller pieces to be inhaled deeper into the lungs and causing more significant symptoms. (Ref: Stump B. "Under the Weather? Men's Health 1999; 14(3) 124-4)

Symptoms of Allergic Rhinitis:

  • sneezing often associated by a runny or clogged nose
  • coughing and postnasal drip
  • itchy eyes, nose and throat
  • allergic shinners (dark circles under eyes caused by augmented blood flow near the sinuses)
  • the "allergic salute" (in a child, persistent upward rubbing of the nose that causes a crease mark on the nose)
  • watering eyes
  • conjunctivitis (an inflammation of the membrane that lines the eyelids, causing red rimmed, swollen eyes, and crusting of the eyelids)

Some people develop bronchial asthma. Asthma can be disabling and at times fatal.

Symptoms of Asthma:

  • coughing
  • wheezing
  • shortness of breath due to a narrowing of the bronchial passages (airways) in the lungs

Mold Allergies

People allergic to molds may complain of symptoms from spring to late fall. The season often peaks from July to late summer. Unlike pollen, the mold season may persist after the first killing frost. Snow cover lowers the outdoor mold count significantly, but does not kill the molds. In the warmest areas of the US molds persist all year and are the cause of so called Perennial allergies. Molds are fungi which reproduce by very small microscopic particles called spores (smaller than pollen). Molds grow easily when there is enough moisture, especially in moist shady areas. Mold spore counts are difficult to use as a guide for daily activities due to the considerable variability of the count in 24 hours due to the close relationship between weather changes and spore releases. It has been found that dry spore type molds release their spore during the day on dry, windy weather and wet spore types release their spores during night and need high humidity, fog or clear.


It is very important to see a doctor for respiratory illnesses that last longer than a week or two. The problem may be an allergy instead of a "cold". Skin testing and blood testing are an adjunct to the diagnosis of allergies.


  • extreme solution: move to a place where the offending substance does not grow
  • remain indoors in the morning, when the outdoor pollen levels are highest
  • sunny windy days are usually troublesome. Wear face masks designed to filter pollen if working outside
  • seashore is an effective retreat for many pollen allergy sufferers
  • mold spores are difficult to avoid. Avoid raking and mowing the lawn.
  • avoid traveling on dry windy days
  • air out summer cabins and rooms that are closed up all winter since they contain a lot of mold spores
  • use air conditioning and filters in the house and car
  • medicines are available for people who cannot avoid airborne allergies. Check with your physician for appropriate care


  1. The Weather and Your Health UK Met. Office
  2. Something in the Air: Airborne Allergens
  3. Weather, Climate, and Human Health
  4. Spring Seasonal Allergies
  5. Breath Easy During Allergy Season
  6. Allergies and genetics
  7. "Are high barometric pressure, low humidity, and diurnal change of temperature related to the onset of asthmatic symptoms?" Prediatr Int 2000 Junl 42(3):272-4.
  8. "Thunderstorm associated asthma: the effect on GP consulations" British Journal Pract. 1997 Oct; 47(423):639-41.