Carbon monoxide is a poison. Can it also be a medicine? Most of the research so far has been conducted in animals; just a few early-stage clinical trials are underway in patients. But the data look promising enough that several companies are jumping into the field, developing ways to deliver small amounts of carbon monoxide to damaged tissues through pills, lotions, beverages, and inhalable gas.
https://www.statnews.com/2017/01/23/carbon-monoxide-medicine/
