Hot tubs and saunas pose no risk to healthy people as long as they are not misused. People with high blood pressure should tolerate saunas well as long as they are not experiencing a hypertensive crisis.
For healthy adults the reduction of blood pressure is a temporary reaction to the body's rise in skin temperature. When a healthy person exits the sauna, blood pressure returns to normal. People with high blood pressure also experience this temporary lowering of blood pressure, but after leaving the sauna their blood pressure can behave abnormally, sometimes rising dramatically.
Saunas have long been used for relaxation, weight loss and stress relief. Saunas have been shown to lower blood pressure, at least temporarily.
Spending 10 minutes in a hot tub should be safe for most treated hypertensive patients.
Hot tubs affect the body in a number of ways. Immersion in hot water causes vasodilatation, the widening of blood vessels. With less restriction to blood flow, hot tubs cause in increase in circulation. Hot tubs also cause in increase in perspiration as the body attempts to cool itself. Hot tubs with a water jet feature can have a massaging effect on the muscles.
The dry heat generated by a sauna can increase circulation. Blood vessels dilate, allowing more blood to circulate through your vessels, bringing nutrients and oxygen to the subcutaneous and surface skin tissue.
People with high blood pressure should not move back and forth between cold water and hot tubs or saunas. This could cause an increase in blood pressure.