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Christmas tree allergy: mould and pollen studies.

Allergists occasionally obtain reports of respiratory symptoms in patients during the Christmas season. These symptoms, including sneezing, wheezing and even skin rashes, may not be severe enough to warrant medical attention, but may be underreported.

In this classic work, the authors systematically investigated some of the potential causes of Christmas tree allergies in patients who they assessed both retrospectively and prospectively. In 1561 patients reviewed retrospectively, only 1.66% reported, unprompted, a seasonal exacerbation of symptoms during Christmas. Prospectively, 1657 patients were questioned from June 1968 to June 1969. Of those with exposure to live Christmas trees (n=1225), 7.6% reported symptoms of allergy.

Clinical features of this seasonal exacerbation were further assessed in 100 patients: 94 from the prospective analysis, and 6 from the retrospective analysis. Most patients presented with symptoms including sneezing, wheezing, transitory rash and blockage of the nose. Symptoms were noted, in 71% of cases, when decorating the tree or within 24 hours. In 15% of cases, onset occurred three to four days after the tree was set up and worsened as the tree dried, which suggested balsam sensitivity was unlikely.

Mould studies from pine and spruce bark showed the presence of Penicillium, Epicoccum and Alternaria, but this did not impact the presence of airborne fungi in the houses where the trees were located. In contrast, pollen studies did demonstrate a release into the air of several types of pollens (weed, grass and tree), which could trigger symptoms. Based on the preponderance of symptoms closely associated with tree decorating, the authors concluded that oleoresins from trees were the most likely cause of Christmas tree allergy.

Very few subsequent studies have reported on this phenomenon, but results from this study suggest that thorough history taking, including questioning patients on variables associated with allergic reactions, can lead to a more complete picture of potential triggers. This allows clinicians to help their patients devise strategies to avoid and manage potential triggers more effectively.

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