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Live Christmas Trees Can Trigger Mold Allergies

FRIDAY Nov. 16, 2007 -- While bringing home a live Christmas tree marks the beginning of the holiday season for many, the mold that thrives on its branches can trigger weeks of suffering for some, a new study shows.

Connecticut researchers have found that the mold count from a live Christmas tree rose to five times the normal level two weeks after the tree was brought indoors, and that can prove problematic for people with mold allergies. Their research was presented this week at the American College of Allergy, Asthma & Immunology annual meeting, in Dallas.

"Christmas trees are another possible source of mold exposure during the holiday season," said study co-author Philip Hemmers, an allergist and immunologist with St. Vincent's Medical Center in Bridgeport, Conn. "Mold allergies peak in the fall, and we see a second peak with a lot of our mold-sensitive patients during the holiday season. Our finding correlates with this second peak of mold sensitivity."

The researchers studied the mold growth of a live Christmas tree in a house in Connecticut. Mold reproduce by releasing spores into the air, so after the live Christmas tree was brought inside the house and decorated, the researchers measured mold spore counts. These counts were taken 12 times over a two-week period between Dec. 24 and Jan. 6. The researchers did not assess the types of mold or whether these molds triggered allergic symptoms in people living in the house.

The study found that the mold spore count was 800 spores per square meter (m3) for the first three days. Normal spore counts are less than 1,000 spores/m3, said Hemmers. However, the spore count rose after day four, reaching a maximum of 5,000 spores/m3 by day 14.

"This mold spore count is five times above normal. These high levels have been correlated with allergic rhinitis and an increased rate of asthma symptoms and asthma-related hospitalization in other studies," said Hemmers. "So if you don't feel well during the holidays, consider the Christmas tree as a possible source of allergies."

Hemmers recommended that people with mold sensitivity keep a live Christmas tree in the house for only four to seven days. An artificial tree may be a better option for people with mold allergies, he added, but they carry their own set of problems, especially if they've been stored in the attic or basement where they can collect dust and mold.

Although Christmas trees are not a problem for most people with allergies, said Dr. David Khan, an associate professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas, there are things you can do to minimize their impact.

"If one is mold-allergic, running an air cleaner in the same room as the tree could theoretically reduce the mold exposure, but this has not been studied," he said. "For some people who are sensitive to odors, the aroma from the tree, which most people like, could irritate their nose and cause symptoms. For these people, avoiding live trees may be best."

Before people start avoiding live Christmas trees because of their mold growth, more research needs to be done, said Dr. Dennis Ownby, a professor of pediatrics and medicine at the Medical College of Georgia, in Augusta. Since this study only looked at a single tree in one home, more homes with trees should be investigated, as well as the types of mold found and whether those molds trigger allergies. He added that the researchers should also measure mold counts outside the home and correlate those to indoor mold counts.

Hemmers said that the outdoor mold count was likely low, since the study was done during the winter. The research team does plan to do further work this Christmas season by looking at more homes and the types of mold found.

In addition to Christmas trees, there are other potential holiday allergens, said Dr. James Sublett, section chief of Pediatric Allergy at the University of Louisville School of Medicine in Kentucky. These can include foods consumed at holiday parties, such as nuts and shellfish, and Christmas ornaments and lights that have been contaminated with dust or mold.

"Store Christmas decorations in plastic containers that you can wipe off, since cardboard can potentially have mold," he advised. "Also wear a N95 dust mask when bringing stuff out of storage."

More information

For more on holiday allergies, visit the Asthma and Allergy Foundation of America.

Posted: November 2007


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