Recent studies have investigated the correlation between exposure to natural environment, health & quality of life and conditions such as allergies, asthma and stress. Research found a strong connection between lower exposure to natural environment and increase in conditions such as allergies and asthma.
A 2012 Finnish study, published in the Proceeding of the National Academy of Sciences, found a strong connection between lower exposure to natural environment and increase in conditions such as allergies and asthmaThe researchers collected samples from 118 teenagers and found that those living on farms or near the forest had more diverse bacteria on their skin had lower allergen sensitivity compared to those ones who resided in urban areas. In fact, the researchers explain that diversity of bacteria is very important for the normal development and maintenance of the immune system.
They also discovered that different species of bacteria have different functions e.g. Acinetobacter (a type of gammaproteobacterial mostly present in in vegetative environment) was shown to be strongly associated with the development of anti-inflammatory molecules so, the more of these bacteria on the skin the higher is the body’s immunological response to suppress inflammatory responses such as to pollen, animals etc.
Another study, conducted by the OPENspace Research Centre in Scotland and published in the Journal Landscape and Urban Planning, found a strong correlation between levels of cortisol, a hormone released in response to stress, and the amount of green spaces where people lived providing an objective measurement tool for stress levels due to lack of natural environment in the surroundings
The researchers concluded saying "We know that if you live near more green spaces, and you are from a deprived urban population, you are more likely to be healthier," she observed.
Further reading : Hayfever A Natural Approach
Ilkka Hanski et al, Environmental biodiversity, human microbiota, and allergy are interrelated, PNAS May 22, 2012 109 (21) 8334-8339