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Genetics and the Environment Work Together in the Development of Allergies

22Seasonal allergies are responsible for a large part of an allergist’s patient population throughout the year, especially in spring and fall. “Some patients have year-round allergies, but even those people can have peaks in symptoms in the high-pollen seasons,” says Meghan Lemke, MD, of Alabama Allergy & Asthma Center in Birmingham. “Seasonal allergies typically are caused by pollen – tree pollen in spring, grass pollen in summer, and weed pollen in fall. Perennial allergic rhinitis can be caused by house dust mites, pets and molds.”

So why do some people suffer from allergies while others are not affected at all? According to studies, both the environment and genetics play a role. “Some people have more susceptibility to allergies than others, and family history can sometimes be a clue,” Lemke says. “We believe it is complex interplay between genetics and the environment that causes allergies to develop.”

While scientists have long understood that this interplay results in allergic diseases, Lemke and some of her colleagues did a study to determine whether infants with a familial allergic predisposition are more susceptible to the adverse effects of second hand smoke when it comes to the severity of a lower respiratory tract infection (LRTI) such as bronchiolitis.

“Understanding the interplay between genetics and environment is especially important in this area, as infants hospitalized for bronchiolitis have a 30 percent chance of developing persistent wheezing or asthma in the first decade of life,” Lemke says.

Lemke and her colleagues hypothesized that infants with a genetic predisposition for asthma or allergies would be more vulnerable to the effect of an environmental factor such as second hand smoke on the severity of a viral LRTI. Published in 2013, the study followed 451 mother-infant dyads during an infant LRTI. “We found that among infants with a genetic tendency for allergic disease, there was a 23 percent increase in hospital length of stay in infants who were also exposed to second hand smoke. We did not detect any significant difference in those who did not have familial atopy,” she says. “Many more studies are needed to further delineate the combined effect of genetic and environmental factors on the development of allergic diseases, including seasonal allergies.”

Regardless of the cause of allergy, allergists want to provide their patients the most effective treatments available. While a number of available medicines are often effective, Lemke says immunotherapy currently is the best treatment available for some allergy sufferers.

“We give patients injections that contain extracts of different allergens they are allergic to. We give them regularly over a period of time and it helps to improve the patient’s immune system in response to those allergens,” she says. “It is a protective response instead of an allergic response and should lessen symptoms over time.”

Of course, once an allergy is identified, avoiding exposure to that allergen is important when possible. In peak allergy seasons, people allergic to pollens should limit their time outdoors when the pollen count is especially high. Knowing the pollen count before going outdoors can help allergy patients control their reactions.

Regular pollen counts are available to Birmingham area residents thanks to a five-year partnership between Alabama Allergy & Asthma Center and Birmingham-Southern College. Wayne Shew, PhD, Ada Rittenhouse Snavely Professor of Biology at Birmingham-Southern, is responsible for maintaining and reading the monitoring equipment mounted atop the college’s humanities center.

“I collect pollen and mold spores, count them and identify them and report this information to the National Allergy Bureau,” Shew says. “I do this three to five times a week which can help allergy patients stay aware of changing pollen conditions.”

He says the biggest benefit to patients is that they can use this information to know when the pollen levels increase. “When they know the count is high, they can use their antihistamines or stay indoors to reduce their allergy symptoms,” Shew says.

Lemke agrees that being able to know pollen counts is helpful. “To avoid allergic triggers, it is helpful to be able to correlate symptoms to when the pollen count is high,” she says. “Some patients only use medications seasonally, and being able to know when the pollen is high allows me to provide guidance for use of the medicines.”

Lemke encourages physicians to refer allergy patients to an allergist for management of the condition. “It is helpful for patients to find out what they are allergic to so they can avoid triggers in their home or outdoors,” she says. “Immunotherapy is best used under the guidance of an allergist, and many patients will benefit from it.”

By: Ann B. DeBellis

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