August 14 (HealthDay News) -- Even a little stress and anxiety can greatly worsen and extend a person's reaction to common allergens, a new study says.

The finding, to be presented Thursday at the American Psychological Association annual meeting, in Boston, are important, as allergies are the fifth-most-common chronic disease in the United States. The researchers estimated that Americans pay more than $3.4 billion for allergy medications and allergy-related doctor visits annually, and lose about 3.5 million work days a year because of them.

"Allergies are not minor problems," researcher Jan Kiecolt-Glaser, a professor of psychology and psychiatry at Ohio State, said in a news release issued by the university. "A huge number of people suffer from allergies and, while hay fever, for example, is generally not life-threatening, allergy sufferers often also have asthma, which can be deadly."

The study looked at 28 volunteers with a history of hay fever and seasonal allergies. Researchers gave standard allergy prick tests to the volunteers, then measured the raised "wheals" that formed on the arms of the participants before and after they were subjected to stressful situations, such as given a speech and answering a series of math questions. They were tested again the next day as well.

"The wheals on a person who was moderately anxious because of the experiment were 75 percent larger after the experiment, compared to that same person's response on the day when they were not stressed," Kiecolt-Glaser said, signifying a stronger reaction.

"But people who were highly anxious had wheals that were twice as big after they were stressed compared to their response when they were not stressed. Moreover, these same people were four times more likely to have a stronger reaction to the skin test one day later after the stress," she said.

This second-day "late-phase reaction" signals an ongoing and strengthening response to the allergens, the researchers said. It suggests that sufferers may react strongly to other stimuli that previously hadn't caused them to develop an allergic reaction.

Co-investigator Gailen Marshall, a professor of medicine and pediatrics at the University of Mississippi, said late-phase reactions typically do not respond to common allergy treatment, such as antihistamines.

"Late-phase reactions also occur in allergic asthma and can, in the proper settings, be potentially life-threatening. The results of this study should alert practitioners and patients alike to the adverse effects of stress on allergic reactions in the nose, chest, skin and other organs that may seemingly resolve within a few minutes to hours after starting, but may reappear the next day when least expected," he said.

Therefore, people may be setting themselves up to have more persistent allergy issues by being stressed and anxious when allergy attacks begin, Kiecolt-Glaser said.

SOURCE: Ohio State University, news release, Aug. 14, 2008