If you follow the safety guidelines outlined by the manufacturer, a hot tub is usually very safe to use. (Make sure not to heat it above 104°F.) However, there are some groups that should exercise caution before getting in a hot tub. If you’re pregnant or have a heart condition or other health issue, consult your doctor before using a hot tub. Children under five should never use a hot tub, and older children shouldn’t stay in a hot tub for more than five to ten minutes.