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Attack of the allergens
Common foods worsen hayfever symptoms, doctors say
On the Net
American Academy of Allergy, Asthma and Immunology: www.aaaai.org
By Linda A. Johnson ~ The Associated Press
Hayfever sufferers know all too well the miseries of the late-summer ragweed season: runny nose, sneezing and itchy, watery eyes.
What most don't know is that among some people allergic to ragweed, common fruits and chamomile can worsen symptoms temporarily. In rare cases, it can cause a life-threatening reaction called anaphylactic shock.
That's because allergy-stimulating proteins in pollens released by plants are chemically similar or even identical to those in some fruits and vegetables, said Dr. Leonard Bielory, director of the Asthma and Allergy Research Center at the University of Medicine and Dentistry of New Jersey.
Ragweed season began in much of the country Aug. 15. Some people allergic to ragweed feel symptoms spike suddenly after eating honeydew melon, cantaloupe or bananas. Symptoms can also spike after drinking chamomile tea, using soap or face powder containing chamomile, or taking herbal supplements that include it.
This protein cross-reaction, in 1987 dubbed "oral allergy syndrome," causes itching and tingling of the mouth, lips, throat and even ears, and, in more severe cases, swelling of tissue. Chamomile causes the most severe reactions, occasionally including anaphylactic shock, a severe, often fatal systemic immune reaction.
"The chamomile-ragweed association has been known for a long time, because in the plant kingdom they're in the same family," said Bielory, who is teaching doctors about such cross-reactions.
Other foods also can exacerbate ragweed allergies, including cucumber, zucchini and watermelon.
The number of people suffering from allergies has been rising, surveys find, partly because of pollution and global warming which has increased levels of carbon dioxide in the air. More carbon dioxide, which plants breathe, dramatically increases the release of pollen, according to some research.
Besides ragweed, mold spores are at very high levels, adding to the misery of many allergy sufferers. The stretch of dry, hot weather with little rain has made mold release its spores well ahead of the usual time, the first cold snap in the fall, Bielory said.
At least 20 percent of Americans suffer from allergies, and ragweed ranks No. 1. There are no firm data on how many people allergic to ragweed suffer cross-reactions from foods during ragweed season, partly because patients often neglect to tell doctors, said Dr. John W. Yunginger, a pediatric allergy specialist retired from the Mayo Clinic. But it's believed to be a minority of patients.
"We've known about some of these (cross-reactions) for over 10 or 15 years," he said. "What is new is the fact that they're slowly tracking down the proteins that are involved."
While that research should bring doctors and patients a better understanding of the problem, it's unlikely to lead to better treatment, Yunginger said.
"It's popping scientific wheelies," he said.
In Europe, where doctors have done more research on the issue, some treat patients' food allergies through immunotherapy using the related plant pollen. In immunotherapy, patients receive weekly shots containing gradually increasing doses of the offending allergen for a year to 18 months to desensitize their immune system. Individual case reports by Yunginger and a few other researchers showed the approach has cured the hayfever and food allergy.
The limited research has not convinced American doctors, and the strategy is rarely used here, said Dr. Donald Pulver, an asthma specialist and assistant professor at the University of Rochester.
That leaves avoiding the offending foods as the best strategy for preventing problems. Antihistamine pills help in some patients, but don't counter most of the allergy-triggering chemicals in pollen, so major medical groups recommend nasal sprays containing low doses of steroids as the best treatment, Pulver said.
"They are now the first-line treatment for airway disease," proven safe in children as young as four, he said.
Yunginger said the one ray of hope for patients is that hayfever burns out in middle age in most people as immune system reactions decline.