A sweat lodge is a shamanic ceremony, where a group of people sits together in a small hut in cycles of one hour. Inside the hut it's 90 degrees Celsius. This temperature is reached by putting fire-heated stones in the center.
Sweat lodge ceremonies (also named temazcal or temascal) are leaded by shamans. In the ceremony, rituals such as singing, praying and mantra chanting are performed by the group. You may know that meditation practice changes our state of consciousness. The mantras, and the singing and praying also bring the participants into a meditative trance, which has a consciousness altering effect.
The direct effects of the heat
By remaining in this incredibly hot environment, the body temperature rises. This brings the body in a feverish state. If you've ever had a fever, you may have experienced the hallucinating effects brought along by fever. The combination of meditation and being exposed to high temperatures can result in powerful spiritual experiences, comparable to those induced by psychedelics.
Add to that, the hardships of a sweat lodge ceremony can be so extreme, that at a certain point you have no choice other but giving into the experience. All kinds of emotions may be released now. A properly guided ceremony can be helpful when you suffer from stress, PTSD, alcoholism and other psychic disorders. 
Sweat lodge ceremonies have a spiritual significance, but staying in a sweat lodge also has a beneficial effect on the body's conditions. It stimulates detoxification, lowers the blood pressure, fights infections and it may help rise the blood's oxygen level.
Fifteenth century explorers brought us the sweat lodge and syphilis
From history we know that one disease in particular could be treated by a sweat lodge. When Columbus arrived in North America in the fifteenth century, the explorers got introduced to sweat lodges. But they also got into contact with the syphilis bacteria. The seamen brought this bacteria to Europe, where an syphilis epidemic broke out. There was no known remedy for this disease, and many Europeans died from it. However, some patients did get cured: those who travelled back with the explorers to North America and underwent sweat lodge ceremonies
The Big Spirit heals
The indigenous people had very extended treatment for syphilis, consisting of a diet, antibiotic herbs and many consecutive sweat lodge ceremonies.
In those days, people were not fully aware that diseases were caused by bacteria. The indigenous cultures saw diseases as spirits, that came over to you whenever you had a life lesson to learn. That life lesson could be learned in sweat lodges, where you got into contact with the Big Spirit. As soon as you learned the lesson, your healing started.
Healing at 42°C
From a scientific perspective there's another explanation of how sweat lodge rituals were able to cure syphilis. The bacteria that's responsible for syphilis is a spirochete. It's a very small bacteria with the shape of a snake. Scientific research has shown that the spirochete dies at 42°C. Also, antibiotics are more effective at high temperatures.  Sweat lodges could even make your body temperature rise up to 42°C, and the antibiotic herbs used by the indigenous cultures have proven to be effective against spirochetes.
Westerners are often sceptical about shamanistic healing, but many of these rituals have in fact scientifically proven healing effects. Our encyclopaedia article on kambo is a fascinating example.
If you're healthy, you may want to try a sweat lodge ceremony for the spiritual experience. It's in all cases advisable to read more on this topic beforehand, because a sweat lodge ceremony requires knowledge and caution.
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