Nettlesome weed causes asthma for some.

Nettlesome weed causes asthma for some

A woman sought help from allergist Herbert S. Kaufman of San Francisco, complaining of asthma that flared when she walked into her backyard. Conventional allergy skin testing failed to identify the cause of her symptoms. Kaufman was stumped until the woman handed him a bag full of weeds plucked from her yard.

Kaufman gave her a test that measures breathing ability, then repeated the test after she had inhaled from the bag of freshly harvested plants. Immediately, the wheezing symptoms of asthma returned. Fifteen minutes later, Kaufman found the patient's breathing ability had dropped by 25 percent.

What was in the bag? A perennial weed called Parietaria judaica, which belongs to the nettle family and flourishes in many parts of Europe. A few months earlier, Kaufman had encountered P. judaica by chance during a visit to Florence, where an allergist had identified it as a weed whose pollen causes much misery in Italy, Greece, Portugal, Spain and France, making it the European equivalent of ragweed. Kaufman says there are no previous scientific reports of Parientaria-linked respiratory allergy among U.S. patients.

That initial case led the private practitioner to study 100 people aged 16 to 63 who suffer seasonal respiratory allergy. Kaufman pricked their skin with extracts of two nearly identical species known to cause respiratory allergy in Europe, P. judaica and P. officinalis, and found that eight people reacted to the pollen. His study, reported in the March ANNALS OF ALLERGY, turned up Parietaria-sensitive patients from Fresno to Pebble Beach, Calif.

"It's in Golden Gate Park. It's in my backyard in San Francisco," Kaufman told SCINCE NEWS. I'm not saying that this is the predominant cause of respiratory allergy in California; I'm saying it's contributor, and in some cases it can be a major contributor."

The finding raises a question about whether P.judaica, P. officinalis and related species cause allergic reactions in other parts of the United States. A Geographical Atlas of World Weeds (Holm et al., 1979, John Wiley & Sons) lists only two Parietaria species in the united States--P. floridana and P. pensylvanica--but a weed hunt by Kaufman revealed P. judaica and P. officinalis thriving in San Francisco. He says a total of five Parietaria species may grow in the United States, primarily in warm, coastal regions. Allergists don't yet know the clinical significance of P. floridana and P. pensylvania, Kaufman says.

Other researchers must verify this small study indicating that some Parietaria pollens have caused allergic reactions in the United States, cautions Lawrence J. Prograis at the National Institute of Allergy and Infectious Diseases in Bethesda, Md.

"The question," Prograis says, "is how significant is this going to be?" He notes that many allergens cause the familiar symptoms of wheezing and sneezing in only a small number of people.

Kaufman admits his study does not address the larger question of whether the weed is a major cause of respiratory allergy in the United States as a whole. But for now, he believes California physicians should be alerted to the possibility of Parietaria-caused wheezing from October through December, when the suspect allergen blooms.