For the one in three people who are now thought to suffer from some form of allergy, newspaper reports of a possible link between allergic rhinitis and Parkinson's disease make worrying reading. Headlines such as 'Allergies linked to Parkinson's disease' (Times Online, 8 August 2006) and 'Does sneezing point to Parkinson's?' (Daily Mail, 8 August 2006) arose from a paper published in the 8 August issue of the journal Neurology by investigators at the Mayo Clinic College of Medicine, in Rochester, Minnesota (USA).

This case–control study looked at 196 people who developed Parkinson's disease, matched with 196 people of similar age and gender who did not, over a 20-year period. The authors found that those with allergic rhinitis were 2.9-fold more likely to develop Parkinson's disease later in life. According to the lead author, James Bower, people with allergies might be “more likely to mount an immune response in the brain as well ... This may release certain chemicals in the brain and inadvertently kill brain cells”.

Although the authors emphasized that the study did not prove that allergies can cause Parkinson's disease and showed only that there is an association between the two conditions, others feel that the study is misleading. As reported in the Guardian Unlimited (8 August 2006), the Parkinson's Disease Society (UK) has pointed out that, on the scale of clinical trials, 200 cases is a tiny number from which to draw conclusions. Kieran Breen, Director of Research of the society, thinks that reports of a causal link are “the biggest scare-mongering thing you can think of.” Instead, he says that the study “may demonstrate that allergic rhinitis may be one of the effects of Parkinson's.” (New Scientist, 8 August 2006).