It’s once again time to run my annual column on allergies. Many of our readers are probably already cursing the annual return of allergy symptoms. The pollen levels in Indiana are already ramping up as spring (hopefully) arrives for good.
Allergies are a major problem for many people. When allergy sufferers are asked about their quality of life, they generally rate allergies as more bothersome than heart disease and sometimes even cancer. There are many causes of allergies, but I want to focus on the seasonal type.
Seasonal allergies are caused by pollen. Pollen actually contains the plant’s male DNA; it is analogous to sperm in animals. The goal of any biologic organism is to spread its genes as far and wide as possible. Pollen is the perfect vehicle to accomplish this task.
There are two main categories of pollen – anemophilous (wind-loving) and entomophilous (insect-loving). Anemophilous pollen is very lightweight which allows it to move great distances, particularly on windy days. In fact, engineers have used the geometric shapes of some of these pollen grains to shape golf ball dimples to help them fly farther. Anemophilous pollen is produced by trees, grasses and weeds.
Entomophilous pollen is produced primarily in plants that bear flowers. It is much heavier and stickier, allowing it to be picked up and spread about by insects. These pollens are much less likely to cause human allergies since they are not typically blown into noses by the wind.
Plants produce and release pollens at various times of the year, hence the “seasonal” nature of allergies. Trees in Indiana start pollinating in late February and usually end sometime in May. Each species of tree pollinates for around one to two weeks. Right now, the predominant pollen in central Indiana is from Maple, Juniper and Poplar trees.
Grasses start pollinating in April and continue on through May. Hoosiers then get a break until about mid-August when ragweed starts up and continues until sometime in October. The allergy season has become longer over the past 15 years, starting two to three weeks earlier and lasting two to three weeks longer. This is generally felt to be due to warming from climate change.
Pollen grains contain proteins on their surfaces that attach to the tissues on the inside of the nose. In order to develop allergies, a person’s immune system must be genetically programmed to recognize these proteins as foreign invaders. This occurs in about 40 percent of people.
The immune systems of these people react to these proteins by creating a specific class of antibodies called immunoglobulin E (IgE). The process of developing IgE in sufficient quantities to cause problems can take anywhere from two to ten years. This is why people often don’t develop allergies until they have been exposed to an allergen for a number of years (the family dog’s skin dander for instance).
When IgE is produced, it attaches to the cell membranes of mast cells where it sits, waiting to do its job. When an allergen like pollen finds its way to a mast cell coated with IgE specific to the allergen, it binds to the IgE causing the mast cell, through a process called degranulation, to release various substances that cause allergy symptoms.
One of the most common molecules released by mast cells is histamine. It causes the typical nasal symptoms of congestion and watery discharge as well as red, itchy, watery eyes and perhaps wheezing. These physical effects are all designed to do one thing – blow or wash the allergen out of the body.
Diagnosis of pollen allergies is fairly straightforward. The offending agent can often be determined based on the time of year a patient develops symptoms. Sometimes the services of an allergist are required to do skin or blood testing to get more specific information.
There are numerous treatments for allergies. Avoidance is strongly recommended – stay indoors when possible (particularly on windy days) and run the air conditioning instead of opening the windows. Saline (salt water) rinses can be very effective at rinsing pollen out of the nose. This can be done using commercial products such as a neti pot or squeeze bottle such as Sinus Rinse®.
Antihistamines are a mainstay of treatment. These medications block the release of histamine by mast cells. There are numerous antihistamines available both off the shelf and by prescription. Older antihistamines like Benadryl® often cause drowsiness, but are still very effective. Newer medications like Claritin® (loratadine), Allegra® (fexofenadine), Zyrtec® (cetirizine) and XYZAL® (levocetirizine) are generally less sedating but are more expensive.
Other treatments are also available such as nasal steroid sprays like Flonase® (fluticasone) and sprays to keep mast cells from degranulating. Severe sufferers, or those who fail other therapies, may need to receive allergy shots or allergy serum under to help train the immune system to reduce the intensity of its reaction to the offending agent(s).