THURSDAY, May 1 (HealthDay News) -- Have asthma or think you might? Then May is the month for you to get a handle on this common breathing disease.

Free asthma screenings are scheduled to be held at 250 locations across the United States as part of National Asthma and Allergy Awareness Month. The American College of Allergy, Asthma & Immunology sponsors the annual effort, and this year the emphasis is on helping those already diagnosed with asthma to get it under control as best they can.

In recent months, the National Heart, Lung, and Blood Institute (NHLBI) put out new guidelines highlighting the importance of asthma control, including daily monitoring and proper medication use to treat symptoms and prevent severe attacks from occurring. This came in light of research showing that many people with asthma are suffering more than they need to from the disease.

"The government guidelines emphasize that undiagnosed or inadequately treated asthma worsens the severity of the disease," allergist John Winder, chairman of the Nationwide Asthma Screening Program, said in a prepared statement. "The screening program gives patients who are still having breathing problems a chance to meet with an allergist, discuss their symptoms and learn how to feel better."

More than 22 million Americans, including 6.5 million children, have asthma -- a chronic inflammation of the airways in the lungs. Asthma attacks, which claim nearly 4,000 lives a year, are often triggered by allergens -- these include pollen, dust, animal dander, certain drugs and food additives -- lung infections, or even physical exertion. While the disease's exact cause remains unknown, many treatments are available to keep it in check.

"An asthma 'attack' isn't the only sign of trouble. A cough that bothers you at night, shortness of breath, colds that go to your chest -- these can all be symptoms of asthma. But few people recognize them or that they are a sign of under-treated disease," Winder said. "No one with asthma should have to suffer. Anyone who is experiencing breathing problems or making compromises to live with their condition should attend a free screening and find out how to take control."

The screenings will be overseen by allergists, who are asthma specialists, and done in coordination with local doctors and allied health professionals. During a screening, participants will answer several questions about their breathing issues, take a lung function test that involves blowing into a tube, and meet with an allergist to determine whether a more thorough exam and diagnosis is needed.

The program has screened more than 108,000 people over the years, and more than half of those were referred for further diagnosis.

A list of free asthma screening locations and dates, online versions of the breathing questionnaires, and more information on treating and controlling asthma are on the ACAAI Web site at www.acaai.org.

More information

The National Heart, Lung, and Blood Institute has more information about controlling and treating asthma.

WEDNESDAY, April 30 (HealthDay News) -- Young children who live in neighborhoods with lots of trees have lower rates of asthma than children who reside in areas with fewer trees, a new study finds.

Researchers looked at asthma rates among children aged 4 to 5, and asthma-related hospital admissions for children up to age 15, in 42 service districts of New York City. Asthma is the leading cause of hospital admission among children aged 15 and younger in the city.

The researchers compared the medical data to information about the number of trees in each of the districts, along with sources of pollution, population density, and racial and ethnic composition.

Nine percent of the young children in the study had asthma, and the city had an average of 613 trees per square kilometer. Asthma rates decreased by almost one-quarter for every standard deviation increase in tree density, equivalent to 343 trees per square kilometer, the study found. This pattern held true even after the researchers factored in sources of pollution, socioeconomic status and population density.

However, there was no association between tree density and asthma-related admissions to hospital among older children.

The results don't mean that tree density in a neighborhood is directly related to asthma rates among children, said the researchers, who added that trees may help reduce asthma rates by encouraging children to play outdoors more or by improving air quality.

The study was published online in the Journal of Epidemiology and Community Health.

The researchers noted that New York City is planning to plant 1 million extra trees by 2017, which could provide an opportunity to study exactly what impact tree density may have on asthma.

More information

The American Lung Association has more about childhood asthma  .

WEDNESDAY, April 16 (HealthDay News) -- Trying to alleviate your asthma by eliminating household dust? Forget about it, a new study suggests.

A comprehensive review of 54 dust-control strategy studies found that none was effective enough in reducing exposure to dust mites that it would improve one's asthma. The methods looked at included using chemicals to kill the little buggers, encasing mattresses and pillows in mite-proof covers, frequently washing linens in hot water or bleach, and even tossing toys, plants and furniture out of a home.

"We can conclude with confidence that there is no need to buy expensive vacuum cleaners or mattress covers or to use chemical methods against house dust mites, because these treatments do not work," study author Peter Gotzsche, director of The Nordic Cochrane Centre in Copenhagen, Denmark, said in a prepared statement.

The review was just published in The Cochrane Library.

Dust mites are microscopic arthropods that carry allergens that irritate bronchial passages and trigger asthma attacks. For years, people have tried to defeat dust mites, but they apparently outnumber and outmaneuver human ingenuity.

"If you are wondering why it is that mattress covers and the other strategies are not effective, the likely answer is that all these treatments do not have a large enough effect on the occurrence of allergens from house dust mites," Gotzsche said. "The level of allergens is so high in most homes that what remains after the treatment is still high enough to cause asthma attacks."

Asthma attacks can be brought on in mite-sensitive people even when allergen levels are very low. For example, while some of the anti-dust methods reviewed cut allergen levels in half, even 90 percent elimination proved inadequate to help many asthma sufferers, Gotzsche said.

The review, Gotzsche said, shows people are being mislead by the 2007 U.S. guidelines from the National Asthma Education and Prevention program. The program recommends actions such as putting mattresses and pillows in dust-proof encasings, and weekly hot water washings of sheets, blankets and stuffed toys.

"Reviews and guidelines should reflect the facts," he said. "It is difficult, perhaps, to realize that we cannot really do anything, but there is no evidence to support these guidelines, and they are misleading. It is about time specialists start becoming honest with patients."

More information

The National Heart, Lung, and Blood Institute has more about the causes of asthma.