[Forests and allergies]

Abstract

Objective: Many research papers have addressed the beneficial qualities of forests in promoting mental and physical health. However, we should also be clear that forest environments could have detrimental effects. Some of them, which are of allergic nature, have hitherto been largely neglected.

Methods: A comprehensive literature search has allowed us to achieve an initial synthesis on this matter. The emphasis was on temperate forests, especially on French forests.

Results: Anemophilous pollen from deciduous trees is the major factor causing respiratory allergies in connection with forests. The risks are focused between mid-winter and late spring. Ash, hornbeam and birch pollen and, more incidentally, oak and beech pollen induce allergic reactions not only in the forests, but also at great distances. As a result of its high humidity and because decaying organic matter is very abundant, the forest environment presents also a breeding ground for mould growth. Accordingly, fungal spores can lead to allergic manifestations recalling pollinosis. Lastly, the "other" allergies mainly include contact dermatitis symptoms, which affect wood workers first and foremost. However, the pine processionary moth, whose zone of infestation is rapidly spreading northwards and whose setae contain several relevant allergens, represents one particular case.

Conclusion: Allergic reactions observed in forests or originating in forests are sufficiently frequent to justify to set up a wide-reaching system for aerobiological and epidemiological monitoring.