Contact with nature may prevent allergies

Author: University of Helsinki

Date: Aug 2012

The increased frequency of allergies and asthma among city dwellers compared to people living in the countryside may result from decreased biodiversity. Broad contact with nature may have far-reaching benefits.

Plodding through muddy ditches and trudging regularly along forest trails may decrease one’s risk of developing allergies, as certain soil and plant bacteria can enhance the immune system when living on the skin.

Reducing the risk of allergy through soil and plant contact

Ilkka Hanski from the Department of Biosciences, University of Helsinki and Tari Haahtela from the HUCH Skin and Allergy Hospital as well as their team have studied how infrequent contact with nature rich in biodiversity affects the variety of beneficial bacteria thriving on the skin and humans’ sensitivity to allergens. The team studied 118 randomly selected schoolchildren in Eastern Finland.

The results indicate that diverse activities involving soil and plants decrease the risk of developing allergies.

?Young people living in an area with plenty of forests and farmland had more diverse bacteria on their skin than those living in a built-up environment and near waterways. Young people living in the countryside were also less sensitive to allergens,? Hanski concludes.

Beneficial bacteria on the skin enhance the immune system?

The range of bacteria living on the skin of healthy young people differed from that on the skin of people sensitive to allergens. The sensitised schoolchildren had a more limited selection of gammaproteobacteria.

In addition, a significant correlation was found between the abundance of bacteria belonging to the Acinetobacter genus, a type of gammaproteobacteria, and the level of anti-inflammatory interleukin-10 cytokine found in blood. Gammaproteobacteria living on the skin may in fact stimulate cells to produce this molecule which enhances the body’s immune system.

Gammaproteobacteria reside in abundance on, for example, plant surfaces. They are also found on grass pollen particles.

?This project has been particularly exciting, because it combines knowledge from various fields, ranging from the structure of the living environment to bacterial communities on the skin and the operation of the immune system,? Hanski says. ?These are all extremely complex systems. It was a great surprise that the results showed strong evidence of connections between biodiversity, bacterial communities on the skin and sensitivity to allergens.?

The article presenting these results was published this week in the PNAS journal.

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