Can You Smell That Smell?

The minerals that make hot springs soaks so good for your health—sulfur in particular—can also generate an egg-like scent. The minerals are dissolved by the warm water as it comes to the surface from deep underground, so the amount of sulfur in the soil makes a difference. One especially acidic spring in Yellowstone National Park is even known as the Sulphur Canyon, and some visitors have joked that the park should be called Smellowstone. More than a century ago, hot springs resorts even provided a choice of Nasal Rebreathers to protect their guests’ sensitive noses from the scent.

It’s not actually the sulfur that creates the smell. Bacteria, especially desulfovibrio vulgaris, that feed on the sulfides in the water and help convert it to hydrogen sulfide is the source of the distinctive aroma associated with hot springs. The bacteria are anaerobic, meaning that they do not thrive when exposed to air, so water that is aerated has a more mild scent. The hotter the water, the more dissolved minerals it contains, and the faster the water reaches the surface from its source, without exposure to oxygen, the stronger it will smell.

In most cases, the first whiff is the worst and visitors stop noticing it after a while. At Iron Mountain Hot Springs, where a liter of water has about 2,060 milligrams of sulfate, the smell is typically very mild. Remember, sulfur is necessary for life—your body has about 150 grams, more than any other mineral except calcium and phosphorous. In addition to its role in protein-building, metabolism, and other bodily processes, many people consider sulfur beneficial for hair, skin, nails, and connective tissue.

You won’t need a Nasal Rebreather to enjoy the relaxation, fun and health benefits of sulfur at Iron Mountain Hot Springs.