today

Exposure to dirt may be a way to lift mood as well as boost the immune system, UK scientists say. Lung cancer patients treated with "friendly" bacteria normally found in the soil have anecdotally reported improvements in their quality of life.

Mice exposed to the same bacteria made more of the brain's "happy" chemical serotonin, the Bristol University authors authors told the journal Neuroscience and say "They also leave us wondering if we shouldn't all spend more time playing in the dirt."

However, it is also possible that serotonin, and serotonin-boosting antidepressants, end up bolstering immunity to the point that they trigger autoimmune disease where the body attacks itself. So clearly it is best not to jump to conclusions about the merits of dirt, and probably also best to avoid excessive use of antidepressants.