THURSDAY, Dec. 27 (HealthDay News) -- If you wake up due to coughing or have a cough that lasts for weeks, you may have a potentially serious problem that requires medical attention.

"Cough is the most common respiratory symptom for which patients seek medical attention," Dr. Alan B. Goldsobel, chairman of the American Academy of Allergy, Asthma & Immunology's cough committee, said in a prepared statement.

"Cough protects the body by removing mucus and irritating particles from the respiratory tract. Coughing is a useful function and does not always mean there is a problem ...," Goldsobel explained. "However, coughing at night, after going to sleep indicates the need for medical attention."

Common causes of coughing include: viral upper respiratory tract infections; asthma; nasal and sinus disease; stomach and esophageal problems; an inhaled foreign body; habit; and environmental irritants.

People should see an allergist/immunologist if they have:

• a cough that lasts three to eight weeks or more;
• a cough that coexists with asthma;
• coexisting chronic cough and nasal symptoms;
• a chronic cough and tobacco use or exposure.

More information

To learn more about cough and children, visit the American Academy of Allergy, Asthma & Immunology  .

WEDNESDAY, Dec. 26 (HealthDay News) -- Childhood milk and egg allergies may be more persistent and harder to outgrow than they were a generation ago, U.S. researchers report.

In two studies from the Johns Hopkins Children's Center, researchers followed more than 800 youngsters with milk allergy and almost 900 youngsters with egg allergy for more than 13 years.

They found that the allergies often persist well into the school years and beyond.

Earlier research suggested that about 75 percent of children with milk allergy outgrew the allergy by age 3. But the Hopkins researchers found that only 20 percent of children with milk allergy outgrew it by age 4, and 42 percent outgrew it by age 8. By age 16, 79 percent no longer had the allergy.

There were similar findings among the children with egg allergy. Only 4 percent outgrew it by age 4, 37 percent by age 10, and 68 percent by age 16.

The studies were published in the November and December issues of the Journal of Allergy and Clinical Immunology.

"The bad news is that the prognosis for a child with a milk or egg allergy appears to be worse than it was 20 years ago," lead investigator Dr. Robert Wood, head of allergy and immunology at Hopkins Children's, said in a prepared statement. "Not only do more kids have allergies, but fewer of them outgrow their allergies, and those who do, do so later than before."

The findings seem to confirm what many pediatricians have long suspected -- that food allergies diagnosed in recent years behave more unpredictably and aggressively than food allergies in the past.

"We may be dealing with a different disease process than we did 20 years ago. Why this is happening we just don't know," Wood said.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about food allergy.

WEDNESDAY, Dec. 5 (HealthDay News) -- Two real-world studies from Europe demonstrate the health damage done by automotive air pollution, especially the kind emitted by diesel engines.

An 11-year period of improving air quality in Switzerland, which started with some of the cleanest air in Europe, produced measurable benefits in lung function for adults as they aged, according to a report in the Dec. 6 issue of the New England Journal of Medicine.

"Even with small improvements in air quality, you get measurable health benefits," said Dr. Ursula Ackermann-Liebrich, a professor of public health at the University of Basel. "That is true at levels even which are quite low."

And an unusual collaborative study by American and British researchers, reported in the same issue of the journal, showed that people with asthma who walked along a street used by diesel-powered traffic experienced loss of breathing much greater than those who strolled through a traffic-free park.

"The unique feature of this study in real-world conditions was that we have demonstrated that typical urban levels of air pollution with diesel-rich powered vehicles have measurable effects," said Dr. Junfeng Zhang, chairman of environmental and occupational health at the New Jersey School of Public Health and an American member of the research team. "There have been theories or hypotheses of diesel exhaust or particle matter and also laboratory studies with animals, but this was a study in the real world with real people."

The study had 60 adults with mild or moderate asthma walk for two hours along two London locales -- busy, exhaust-filled Oxford Street or the more bucolic Hyde Park.

The Oxford Street walk produced a 5 percent to 6 percent reduction in lung function, "and asthmatics already have compromised lung function," Zhang said.

The reduction in lung function was "significantly larger" than what was measured after the Hyde Park walk and was accompanied by an increase in biomarkers of lung inflammation. The negative effect on the lung was greater than has been seen in animal studies using breathing chambers, Zhang said.

The Swiss study found a decrease in the amount of airborne fine particulate pollutants, a major feature of diesel emissions. That improvement in Swiss air quality was accompanied by a slowing in the rate of the loss of breathing function that occurs as people age, Ackerman-Liebrich said. The journal report attributed the healthful effect to "decreasing exposure to airborne particulates."

"There seems to be something more potent than other forms of air pollution in diesel exhausts," said Dr. Morton Lippman, a professor of environmental medicine at New York University. "It is something many other studies have pointed to."

The issue of diesel pollution is of growing interest because "new diesel technologies are increasingly coming on the market," Lippmann said. Diesel automobiles are much more common in Europe than in the United States but are gaining attention because of their greater fuel efficiency, he noted.

The two studies are welcome because they assess the effect of diesel emissions at relatively low levels, Lippmann said. "That remains a complex issue," he said. "Getting statistically significant information on a small average effect on a large population is not easy. There are a lot of unknowns. Most effects are associated with particles rather than gases in the mixture, but there is no data on which part of the components is particularly nasty."

More information

A national program for cleaner diesel emissions is described by the U.S. Environmental Protection Agency.