People taking cardiovascular drugs that dilate blood vessels. Children under three or four years old. Anyone with a tendency to faint. Alcohol should also be avoided around hot tubs. Drinking can cause blood vessel dilation and fainting.
Skin infections can also be a problem from public hot tubs.
Some bacteria grow readily in a warm environment and can be transmitted from one person to another in the hot water. It is also a good idea to sit in a hot tub with someone else present. This can ensure that you will not faint or fall asleep and drown. Soaking in a hot tub can be very relaxing and help many conditions such as arthritis and chronic pain sufferers. Just be sure how clean the water is and that you are not putting yourself in unnecessary danger.