Page 21 - HCMA Bulletin Summer 2021

Practitioners’ Corner
Tampa Bay Pollen and Mold Seasons
Richard F. Lockey, MD rlockey@usf.edu
“It’s pollen season.” Central Flori- da has a subtropical climate, and trees, grasses and weeds, each pollinate dur- ing predictable months throughout the year. Molds, because of the warm and humid environment, also are present throughout the year. Approx- imately 20% of adults and children have one or more atopic diseases, i.e., allergic rhinitis and conjunctivitis, al-
lergic asthma, atopic eczema, or food allergy. Therefore, there is great interest in what is prevalent in the air and what is caus- ing an allergic problem.
First, pollen is much more important allergenically than are mold and mold spores. Second, these are naturally occurring pollutants, not man-made, which cause various diseases, the worst in the spring tree pollen season, during which time an epidemic of allergic diseases occurs. Third, viral respiratory tract infections, particularly rhinoviruses, can imitate symp- toms of allergic rhinitis, i.e., sneezing, itchy nose, runny nose, stuffy nose, as well as exacerbate asthma. Symptoms and signs from viral infections are usually limited to 7 – 10 days whereas allergic problems persist for months.
In order for a pollen to be confirmed allergenic, Thommen’s Postulates must be fulfilled. First, the pollen must: 1) be wind- borne, 2) occur in large quantities, 3) originate from a plant that is widespread, and 4) contain allergenic components. For example, orange trees are insect (honeybees) and not wind- pollinated, therefore, do not cause allergic diseases. However, oak trees, eleven species of which exist in central Florida, bloom sequentially, from December to mid-May and spew trillions of pollen particles and pollen dust into the air. They are wind- pollinated. The second most important trees are collectively the bald and pond cypress, and red cedar trees, the pollen of which cross-reacts. These trees pollinate from December to March. Trees of secondary importance include Australian pine, bay- berry, mulberry, and others. The “tree or spring pollen season” extends from late November to mid-May, depending on local weather conditions. In some years, oak pollen reaches 6,000 pollen particles per cubic meter of air, guaranteed to exacerbate any person allergic to this tree pollen.
Our second season is the grass season, the primary grasses
being Bahia and Bermuda. Levels of grass pollen are relatively low throughout the entire year, especially compared to tree pollen. Bahia grass, introduced from South America, cross re- acts with Johnson grass, a naturally occurring grass. Bermuda has its own unique allergens.
The third season of the year is the weed season. This season is almost year-round, usually sparing the first several months of the year depending on how cold it becomes and whether a frost occurs. Ragweed is the most important weed followed by dog fennel, lambs quarters, pigweeds, and others.
Molds, because of the warm, humid environment, exist in the air throughout the year, peaking during the summer months and decreasing during the colder months. Mold levels are much higher outdoors than indoors and are not nearly as important allergenically as are pollen.
The Division of Allergy and Immunology, University of South Florida, has a pollen and mold collecting station on the North Tampa Campus. It is part of a North American network called the National Allergy Bureau, sponsored by the American Academy of Allergy Asthma and Immunology. Pollen counting stations in this network are located throughout the country. For example, in Florida there is one in Miami and one in Tampa.
What about other allergens, those indoors that affect aller- gic subjects? Indoor allergens are usually more important than outdoor allergens because they are present year-round. They too are naturally occurring pollutants. The main three are dust mites, in particular, Dermatophagoides pteronyssinus and fari- nae and Blomia tropicalis, the latter of which was first discov- ered in the northern hemisphere by members of the Division, and cat and dog allergens. Dust mite allergens are present in the mite feces and bodies and they are primarily found in bed- rooms and in areas where people spend considerable time. A main food source are the five or so grams of epithelial skin cells which each of us shed weekly.
More and more cats, dogs, and other animals, e.g., ferrets, guinea pigs, pet rats, and gerbils, which are associated with al- lergic diseases, have been introduced into homes making these allergens more or less ubiquitous, no matter what the environ- ment. People transfer cat and dog allergens into all surround- ings, including day care centers, schools, and other indoor envi- ronments. Cat allergens are derived from cat dander and saliva and are probably the most potent of all animal allergens. To
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HCMA BULLETIN, Vol 67, No. 1 – Summer 2021
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