Carbon dioxide contained in water forms bubbles on the skin, which triggers off many reactions in the body. It results in vasodilatation of arteries and skin capillaries, which leads to an increase in the blood supply to the skin and consequently, to lower blood pressure and a lower heart rate. It causes an increase in metabolism, the blood supply to the brain and oxygen intake in the lungs. CO2 baths also have a calming and relaxing effect.