MYCOLOGY


All the presents being placed round the trees.”3


In 1840 the then Queen Victoria married her German cousin Prince Albert, and the knowledge and custom of the Christmas tree use during the festive period became fashionable and widespread with middle class families of the time. In 1842 newspaper advertisements associated children and gift-giving traditions, and the illustrated book The Christmas Tree describing their use and origin and was placed on sale in December 1844.4


Following this, their use became established. In 1933 the Government introduced restrictions on the importation of foreign trees, which led to a rapid growth of home-grown trees and provided opportunities within this new and emerging market. As of 2013 some eight million trees were grown for the Christmas market, and they are now commonplace in all homes, shops and public places. Christmas trees are usually harvested a few weeks before the festive season and stored in moist environments with many other trees. Moulds can proliferate in these environments, and when moved into the home or office can shed spores and allergens into the immediate atmosphere. With the festive season seemingly elongating each year, their time within storage and subsequently within the home or office is now significant.


Are Christmas trees dangerous? The dangers of Christmas trees have been well documented. In 1856, the Manchester Guardian reported the accidental death of a woman whose dress caught fire as she lit the tapers on a Christmas tree.5


Moreover, the occurrence


of trees falling over due to small children and pets, or electrocution from Christmas tree lights are relatively commonplace. The association with respiratory infection and allergic symptoms of trees in dwellings have been well documented.6-8


In 1970 Wise reported


on a retrospective study of 1,657 allergic patients, with respiratory and skin allergies to conifers occurring in 7% of cases. The seasonal syndrome included sneezing, wheezing and transitory skin rashes which occurred within 24 hours of tree exposure. Mould and pollen studies were carried out with trees containing significant levels of Penicillium,


Penicillium was among the most common isolates among a total 53 individual mould types identified via microscopy, culture and molecular methods from 26 tree samples in one study.


Epicoccum and Alternia spp. Although no evidence of airborne spread was observed.6


A later study in 2007 indicated


the level of airborne mould spores within an apartment increased from 800 per square cubic metre before introduction of a live conifer, to 5,000 spores per cubic metre after 14 days. Unfortunately spore culture and identification was not carried out in this study.8


To rectify this, staff at


the Department of Paediatrics at Upstate Medical University New York, harvested samples from their live Christmas trees at home for analysis. Results via microscopy, culture and molecular methods identified 53 individual mould types from 26 tree samples. The most common isolates included Aspergillus, Penicillium, Cladosporium, and Alternaria spp.8


Each of these are well known


allergens and have been shown to increase both respiratory and allergy symptoms in susceptible patients. The evidence described above proves that live Christmas trees can carry pathogenic fungal spores and moulds, which can proliferate in centrally heated homes and offices. As already indicated studies suggest organism counts can increase significantly within a two-week period. Furthermore, the 53 species of fungi identified were found on 70% of the trees.


In addition to potentially harbouring fungi, live Christmas trees may also be


Epidemiological analysis indicates that 13% of the US population are affected by mould allergies


30


responsible for introducing additional potentially harmful effects within the house or office:7 n Dust mites may be introduced via Christmas trees, although they do not have a preference for them. While cleaning the tree may remove some, it is unlikely to remove all.


n Ivy often grows around Christmas trees before they are harvested and contains the resin urushiol, which can cause an itchy red rash on touch, resulting in the term ‘poison ivy’. Residual resin can be left on the bark of the tree which may cause the rash when handled.


n Fresh scent of pine from a Christmas tree comes from the chemical terpene, found in the sap of fir trees. Terpene can irritate skin and may cause contact dermatitis, which can cause an itchy, red rash on direct contact.


n Additionally, the spraying of artificial snow or ‘flocking’ can also irritate the lungs as small particles can be inhaled, and trigger allergies and asthma.


Impact of fungal infections Fungi and subspecies moulds are ubiquitous in nature, and their potential to cause disease is well understood. There are over 200,000 species of fungi, which include moulds, yeasts, mushrooms, lichens and truffles. Only about 300 fungi are considered pathogenic to man by the allergens and mycotoxins they produce. Others have been found to provide significant benefits. Most of us like eating mushrooms; however, eating the wrong type can be highly toxigenic and even fatal. Moreover, some fungi, for example Cladosporium bantiana, are highly


DECEMBER 2024 WWW.PATHOLOGYINPRACTICE.COM


Penicillium mould, spore production, SEM. David Gregory & Debbie Marshall. Source: Wellcome Collection.


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