There is much discussion currently about the microbiome. Rebecca Parker discusses why horse people seem to be made of tougher stuff and brings in the hygiene hypothesis, microbes and the inherent exercise in her article.
She also references the benefits of being outdoors and the serenity it takes to work with horses.
Source: Horse Network, June 13, 2017.
Where do we find these helpful microbes? In dirt, for one! When we eat food straight from the ground, with not completely sterilized hands or just through the process of being outside covered in mud, we inadvertently ingest good bacteria. It is also found in high (and more palatable) quantities in fermented foods and probiotic yogurts. Exposure to dirt and bacteria is just one reason equestrians tend to get ill less often, though.
INSIGHTS: I related to this story on many levels. Many animal health pros will too. Parker offers perspectives worth considering.