The Season of Sneezing
It’s once again time to run my annual column on allergies. Some of our readers are likely already cursing the annual return of allergy symptoms. Tree pollen levels of maple, ash, and birch are high and climbing. Spring allergy symptoms can make it even more difficult to differentiate who might have an upper respiratory infection, COVID-19, or just run-of-the-mill allergy symptoms.
Seasonal allergies are a major problem for many people. When allergy sufferers are asked about their quality of life, they often rate allergies as more bothersome than heart disease and sometimes even cancer. Many different things cause allergies; here I will focus on the seasonal type.
Seasonal allergies are caused by pollen. Pollen contains the male genetic material of plants; it is analogous to sperm in animals. One of the main jobs of any organism is to disseminate its genetic material as far and wide as possible to mix with that of others in the species in order to improve fitness and survival. Pollen accomplishes this task in exquisite fashion.
There are two main categories of pollen: anemophilous (wind-loving) and entomophilous (insect-loving). Anemophilous pollen is very lightweight, allowing it to move great distances, particularly on windy days. It is produced by trees, grasses, and weeds. Golf ball engineers even utilize biomimicry of pollen grains to design the dimples on balls to help them fly farther.
Entomophilous pollen is produced primarily by flowering plants. It is much heavier and stickier, allowing it to be picked up and spread by pollinators such as bees. The loss of pollinating insects due to insecticide use and climate change is a real threat to these plants. Entomophilous pollens are much less likely to cause allergies since they are not typically inhaled or blown into noses and eyes by the wind.
Plants release pollen at various times of the year, hence the “seasonal” nature of allergies. Trees in Indiana start pollinating in late February and usually end by May. Each species of tree pollinates for about one to two weeks.
Grasses begin in April and continue through May. Hoosiers then get a brief reprieve until mid-August when ragweed starts up and continues until sometime in October. The allergy season has become longer over the past two decades, starting about three weeks earlier and lasting two to three weeks longer. This is very likely due to warming from climate change.
Pollen grains contain proteins on their surfaces that bind to the tissues of the eyes and inside the nose. To develop allergies, a person must be genetically programmed for their immune system to recognize these proteins as foreign invaders. This is the case in about 40 percent of people.
The immune system responds by creating a specific class of antibodies called immunoglobulin E (IgE). It can take two to ten years of exposure to an allergen to develop enough IgE to cause symptoms. This explains why some people suddenly develop an allergy to a pet they have had for years.
When IgE is produced, it attaches to specialized mast cells, where it sits waiting to respond. When pollen encounters a mast cell coated with IgE specific to it, it binds and causes the cell to release substances that trigger allergy symptoms.
One of the primary molecules released by mast cells is histamine. It causes typical nasal symptoms like congestion and watery discharge, along with red, itchy, watery eyes, and sometimes wheezing. These responses are meant to expel the allergen from the body through sneezing, coughing, or tearing.
Diagnosing pollen allergies is usually straightforward. The likely culprit can often be identified based on the timing of symptoms. Sometimes, an allergist may perform skin or blood tests to determine specific allergens.
There are numerous treatments available. Avoidance is the best prevention strategy: stay indoors when possible, especially on windy days, and use air conditioning rather than opening windows. Use high-quality filters in the home ventilation system. Saline rinses are effective at removing pollen from the nose. This can be done using products such as a Neti Pot or a squeeze bottle like Sinus Rinse®.
Antihistamines are also a cornerstone of treatment. They block the effects of histamine. Many are available over-the-counter or by prescription. Older antihistamines like Benadryl® (diphenhydramine) often cause drowsiness but are effective. Newer options like Claritin® (loratadine), Allegra® (fexofenadine), Zyrtec® (cetirizine), and Xyzal® (levocetirizine) are typically less sedating but may cost more.
Other treatments include nasal steroid sprays such as Flonase® (fluticasone), as well as sprays that stabilize mast cells. For those with severe symptoms or who don’t respond to standard therapy, allergy injections or sublingual drops may be necessary to reduce sensitivity over time.