Hot tubs are very, very cozy
Swimming in any body of water exposes you to skin cells, urine, and other contaminants. Pools have a large amount of water to disperse them, but hot tubs hold less water. “You’re bathing in close quarters with however many of your friends are with you,” says Kelly Reynolds, PhD, microbiologist and associate professor in the public health college of the University of Arizona. With less water to dilute any contaminants, the concentration is higher in a hot tub.