Carbon Dioxide Bath Simply Explained

1. What It Is About

In a carbon dioxide bath, the body is immersed wholly or partly in water enriched with carbon dioxide. Carbon dioxide is a gas that also occurs in the air; in technical language it is called CO₂. There are two forms: in a wet bath the gas is dissolved in the water, in a dry bath the gas flows around the skin. The first reports of such baths date from the 19th century, when natural springs with high carbon dioxide content in the water were used. Today the gas is usually added artificially. The gas penetrates the outermost layer of the skin. There it causes the small blood vessels to dilate and more blood to flow through the skin; experts speak of vasodilation. This effect can be measured: the skin becomes warmer and the tissue receives more oxygen. Unlike warm water baths, the primary action here is not the heat but the gas itself. It is absorbed only through the skin.

2. What Studies Show

The best-studied effect is skin perfusion. In an observational study, 46 people over 65 years of age with at least two risk factors for peripheral arterial occlusive disease (pAVK) received ten dry carbon dioxide baths. Before and after treatment, skin temperature at various body sites was measured with a thermal imaging camera. The temperatures changed markedly, indicating improved perfusion 1. There was no control group in this study, and only skin temperature, not the participants’ well-being, was measured.

One report describes a 46-year-old man with a crush injury to the palm caused by heat. For four weeks the hand was repeatedly immersed in a solution containing a very high concentration of carbon dioxide. The wound was also prepared for skin grafting. Afterwards the necrotic tissue had disappeared and the wound bed had been built up sufficiently for skin from the sole of the foot to be grafted onto the palm. The grafted skin healed and the man was able to resume his daily activities without restrictions 2. This is a report of a single patient; no conclusions can be drawn about how others would have fared.

A further study from 2009 monitored people with cardiovascular disease during the baths using long-term ECG recording of the heartbeat over several hours. Heart-rate variability, that is the regularity or irregularity of the intervals between heartbeats, changed. This suggests that the autonomic nervous system, which unconsciously regulates many bodily functions, responds to the bath 3. The number of participants and the direction of the change are not stated in the paper.

There is also a study on hygiene. In one clinic, four patients contracted a hospital-acquired methicillin-resistant pathogen within four weeks. The organism was also found in the bathtub used for carbon dioxide treatment. After stricter cleaning and disinfection protocols were introduced, no further cases occurred 4. A review identified nine additional outbreaks of this type associated with water applications.

3. What Remains Unclear

Of 36 evaluated papers, nine were observational studies and one was a review; controlled human studies are still outstanding. In such studies one group is treated and another is not; only then can it be determined whether the bath really made the difference. It is therefore still only a hypothesis that the improved perfusion translates into less pain, longer walking distance or faster-healing wounds. How long the effect lasts after a bath is also unknown. The applications differ greatly in duration, temperature and gas volume, which makes comparisons difficult. No tested safety precautions exist for home use; one report describes the death of a man who bathed in an airtight bag 5. In facilities with regulated procedures and tested equipment, the application is considered safe.

4. What This Means in Everyday Life

Carbon dioxide baths are used in spa centres and clinics, mainly where improved perfusion is desired. Research on this application is still outstanding: almost always only the skin was measured directly after the bath, for example its temperature. Whether anyone subsequently experiences fewer symptoms has not been examined. It can therefore be said that the bath measurably alters skin perfusion; what this means for the individual is open. One point is practically important: in regulated facilities hygiene is an integral part of the procedure because pathogens can be transmitted via the tubs. What needs to be clarified next is whether the improved perfusion in peripheral arterial disease, open wounds or hypertension also produces perceptible improvements.

All details with study numbers and sources: detailed page on carbon dioxide bath. For children: Carbon dioxide bath for children.