For many years indoor Christmas trees have bee suspected to be a source of allergen induced asthma, rhinitis and respiratory problems during the period from mid December to early January. It was thought that coniferous tree pollen, incidental grass and weed pollens on the tree and oleoresins secreted by Fir trees were to blame. However a recent study in the US, has found that coniferous Christmas trees carry and sustain significant amounts of mould spores. Common allergenic moulds such as Cladosporium, Aspergillus, Alternaria and Penicillium are found in significant amounts on Christmas trees and raise indorr mould levels from 300 to 5000 spores per cubic metre of indoor air. Exposure to the spores trigger chronic respiratory conditions such as allergic asthma, rhino-sinusitis and chronic bronchitis (COPD). Spraying the tree with a mist containing household bleech such as Milton (sodium hypochlorite) kills off moulds and prevents their growth on the trees and subsequent indoor mould contamination.
Reference: Identification of mold on seasonal indoor Coniferous trees. Annals of Allergy, Asthma & Immunology 2011 106:6: 543-544
