Common sense should prevail at all times. Pregnancy and heart conditions should make users particularly aware that prolonged exposure to hot water can cause problems (seek medical advice). Alcohol, particularly to excess, is obviously not to be recommended. Anyone feeling at all uncomfortable for any reason should leave the tub immediately.
We have heard stories of kidney damage to children in the US, where apparently they have laid against a strong water jet for some time. This would be very difficult in our hot tubs, as users are free floating rather than laid back in the pre-determined body moulds of the plastic spas. Some manufacturers imply that the stronger the jet, the better the experience. We don’t – our pumps are accordingly rated for comfort.
Those with sensitive skin also need to consider which sanitising method to use, as with any spa/hot tub.