Common allergic conditions such as asthma and allergic rhinitis may increase the risk of developing Parkinson’s disease, shedding new light on the potential role of the immune system in neurodegenerative disorders.
South Korean researchers shared details of the claim in their paper, “Allergic Disease as a Risk Factor for Parkinson’s Disease: A Possible Role of Eosinophil,” recently published in npj Parkinson’s Disease. The study analyzed data from more than five million adults and found that individuals with certain allergic diseases were significantly more likely to develop Parkinson’s over time. The findings, the authors noted, add to growing evidence that chronic inflammation may contribute to the onset and progression of neurological conditions.
The large-scale cohort study, which followed participants from 2010 to 2019, identified more than 44,000 new cases of Parkinson’s disease among adults aged 40 and older.
According to the results:
- Individuals with asthma had a 16% higher risk of developing Parkinson’s disease.
- Individuals with allergic rhinitis had an 18% higher risk.
- An atopic dermatitis diagnosis, however, showed no significant association with Parkinson’s risk.
The study’s authors noted that the risk increased further among people with multiple allergic conditions.
The study revealed that more frequent healthcare visits for allergy-related issues — used as a proxy for disease severity — were also associated with a greater risk of Parkinson’s. Specifically, participants with three or more allergy-related medical visits per year faced a notably higher likelihood of developing the neurodegenerative condition compared to those with fewer visits, researchers said.
To better understand the biological connection, scientists examined blood samples from Parkinson’s patients and healthy controls. They found that individuals with Parkinson’s had:
- Higher levels of eosinophils and neutrophils
- An increased eosinophil-to-neutrophil ratio
- A greater frequency of eosinophilia, indicating elevated immune activation
According to researchers, these findings further strengthen the hypothesis that immune system dysregulation and systemic inflammation could influence brain health and contribute to Parkinson’s disease.
Although Parkinson’s disease has traditionally been associated with the loss of dopamine-producing neurons in the brain, more recent research has increasingly focused on the role of neuroinflammation, the authors noted. As such, they suggested this new study reinforces the theory that allergic inflammation — long thought to affect primarily the respiratory system or skin — may have broader systemic effects that extend to the brain.
Although the study shows a clear association, researchers cautioned that it does not prove that allergies directly cause Parkinson’s disease. Instead, the findings suggest that chronic immune activation may be one of several contributing factors.
Still, the authors said their findings could have important healthcare implications, including the need to monitor long-term effects of chronic inflammatory conditions, particularly in high-risk individuals, and the development of new preventive strategies targeting inflammation.
Researchers said further research is needed to determine whether managing allergic diseases could more aggressively reduce the risk of Parkinson’s.
