There are two types of heat used in saunas namely dry and wet heat. Wet heat is a type of heat high in humidity, typically 65%, and is commonly employed in steam baths found in spas that tend to operate at temperatures of between 40 degrees Celsius and 50 degrees Celsius. The high moisture content, however, makes them feel much hotter. Saunas on the other hand use dry heat. With moisture content less than 20%, saunas can heat up to 100 degrees Celsius. With less humidity, the conditions are much better than in steam baths and breathing is also much easier. Others may find it a bit too dry so some water may be poured on the stones to increase the moisture content. Some more techno-savvy saunas use infrared for heating and the proponents of this technology tell that it is better since it provides direct heat stimulation and offer deeper tissue penetration. The principle is still the same, nonetheless. Sauna baths a typically between 10-15 minutes and use heat to induce perspiration.
The 10-15 minutes sessions stimulate nerve endings to release acetylcholine which then open the sweat glands found in the skin. This is a the regulatory response as the body sweats to cool off as a result of the heat. The capillaries under the skin dilate which open the pores on the skin to excrete toxins, excess oils and dirt resulting in a glowing skin. When followed up with a shower, it can help remove dead skin. One can release up to a liter of water from a sauna bath and it is therefore important to properly hydrate before getting into a sauna bath for this reason. By sweating, the body rids itself of toxins which are then released through the open pores on the skin.
The heat stimulates the endocrine glands which secrete endorphins, which are our feel good hormones and that is the reason why a sauna bath leave us feeling great. The heart beat increase, without a corresponding increase in blood pressure, to match the elevated blood flow. The dry heat improves lung function and can benefit those with respiratory problems. Wet heat is counter advised for those with pneumonia and other respiratory ailments since the high humidity causes difficulty in breathing. A too dry heat isn't better either as it can damage the protective mucous membrane on the lungs.
Stimulated by the heat, the body's metabolism quickens benefiting the bather with the same perks as those of a mild exercise. The sweating result in weight loss, but there is a danger of dehydration and therefore should not be replaced with weight loss programs such as dieting and exercise. The heating effect on the muscles also relieve muscular aches which combined with the improved blood flow result in a soothing feeling, less stress and better mobility.