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Does your brain need protection from the effects of allergies? Respiratory allergies may cause confusion, depression, sleep problems, and other mental issues.

Summer is the sneezing season. It's the time when the physical symptoms of respiratory allergies--such as itching, dripping, sneezing and wheezing--are an annoying fact of life for more than 40 million Americans. But respiratory allergies, which are caused by inhaling allergens such as dust, pollen, animal dander or mold, may affect not only our bodies, but our minds as well. They have been linked with mental symptoms such as depression, irritability, poor memory and trouble concentrating, something to be aware of if you suffer from allergies.

Experts have identified several possible causes of these mental symptoms, including reactions within the brain to pro-inflammatory chemicals released by the immune system as it combats allergens, the side effects of allergy medications, or the indirect effects of respiratory difficulties, such as sleep deprivation and low brain oxygen levels.



Research suggests that the allergy season in many areas of the country is becoming more severe. Scientists reviewed 15 years of pollen data from eight locations in both the United States and Canada and found that the duration and intensity of ragweed allergies--which affect one in 10 Americans--have grown in northern latitudes with every passing year, probably because of the effects of climate change. In a report published in the Feb. 21, 2011 online issue of the Proceedings of the National Academy of Sciences, the researchers reported that places in the middle of the country and northward had seen the ragweed season steadily lengthen over the period from 1995 to 2009, with longer seasons and higher levels of pollen the more northern the location. Their data indicated that ragweed season was longer by one day in Oklahoma City, 12 days in Madison, Wisconsin, 16 days in Fargo, ND, and 27 days in Saskatoon, Saskatchewan.

"A lengthening allergy season means that people are suffering longer with the distress caused by allergic reactions, and this exacts a toll in terms of both health and economics," says Ottavio Vitolo, MD, a neuropsychiatrist and researcher at MGH's Depression Clinical and Research Program. "People who suffer from allergies often experience sleep problems, low mood, and impairment in their ability to perform basic activities--such as working or driving a car--that may lead to costly mistakes or accidents.

"What's more, increasingly severe allergy seasons may make people with allergies more dependent on allergy medications, and many of these drugs may compound mental symptoms."


Some researchers believe that allergies have a direct physiological impact on brain functioning. According to this theory, allergies cause the release of pro-inflammatory cytokines, proteins released by the immune system to combat allergens. The cytokines, in turn, spur the release of a brain chemical called IL-1 beta, which is associated with feelings of low mood, weakness, lethargy and difficulty concentrating. A direct effect of allergies on brain function may explain one study in which people with hay fever were found to be twice as likely as people without allergies to have been diagnosed with major depression in the previous 12 months.

Even without a direct brain effect, however, respiratory allergies can influence a person's mental functioning, Dr. Vitolo points out.

"The congestion and difficulty breathing that accompanies respiratory allergies may compromise blood oxygen levels in people who suffer from other medical conditions," says Dr. Vitolo. "Allergies can also affect brain functioning by worsening obstructive sleep apnea, thus affecting sleep quality. It is well known that sleep disturbances increase risk for depression and cognitive problems such as poor concentration, diminished verbal fluency, and difficulty with learning and memory.

"Older adults may be more vulnerable to brain effects from allergies than younger people because they are more likely to have existing medical conditions, such as sleep apnea and heart conditions. Narrowed blood vessels associated with cardiovascular problems limit the brain's supply of oxygen, and the congestion caused by allergies intensifies this problem. Older adults are also more likely to have age-related cognitive problems that can be aggravated by stresses on the brain associated with allergies."


Many allergy medications that are effective in reducing the physical symptoms of respiratory allergies may have undesirable mental effects, and older adults may be especially sensitive to these drugs. The long-term use of anticholinergic allergy drugs such as Benadryl, which block a key neurotransmitter, can lead to memory problems. Over-the-counter antihistamine and decongestant drugs, and a number of prescription medications as well, often compound the mental effects of allergies by causing feelings of drowsiness, difficulty focusing, memory impairment, fatigue, sleep disturbances, and other symptoms. Although this is especially true of the older medications, even some of the newer allergy drugs can affect brain function or mood. Given the effects of allergy drugs, Dr. Vitolo advises individuals with symptoms of respiratory allergies to see their physician before self-medicating.

"Doing nothing about serious allergies could be physically and mentally stressful and might lead to other problems," he says. "But treating yourself with over-the-counter drugs can be risky if you have other medical problems, such as asthma, cardiovascular diseases, chronic obstructive pulmonary disease or sleep apnea. That's why it's especially important for older people, individuals with severe allergies, and people with health problems to get a medical assessment and diagnosis before taking allergy drugs."

Your doctor should be able to help you formulate an effective treatment plan that may include determining the cause of allergy symptoms, finding safe and effective non-sedating medications or nasal sprays (for example, the nasal spray NasalCrom or cromolyn) to relieve allergy symptoms, and recommending other treatment options, such as immunotherapy to alter the body's immune response to the allergen. (See What You Can Do.)


You may be able to help decrease the severity of your respiratory allergy and/or reduce mental symptoms on your own by following these suggestions:

* Avoid the allergen as much as possible. For example, if you are allergic to pollen, try to stay indoors and avoid strenuous exercise during peak pollen times. Keep your house dust-free if dust mites set off sneezes.

* Use an air conditioner.

* Use an air filter or dehumidifier to remove airborne allergens, but be sure to have them serviced and cleaned regularly to prevent the buildup of molds and other contaminants.

* Use a saline nasal rinse to help reduce symptoms.

* Consider getting treatment for allergy-related depression that lasts longer than two weeks.
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Publication:Mind, Mood & Memory
Geographic Code:1USA
Date:Jun 1, 2011
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