Carbon dioxide hand baths may help in SSc-related Raynaud’s, study finds

​Baths enriched with CO2 offer low-cost option to boost blood flow in fingers
Written by Andrea Lobo, PhD | March 3, 2026

​Hand baths enriched with carbon dioxide (CO2) — a gas that exists naturally in the atmosphere, and is produced by living things breathing out — can significantly widen blood vessels of the fingers in people with systemic sclerosis (SSc)-associated Raynaud’s phenomenon.

That’s according to a small clinical trial in Germany, which found that warm water hand baths can boost blood flow in the fingers in people with these conditions. By widening tiny blood vessels in the fingers more effectively than warm water alone, the treatment may help ease symptoms that make everyday tasks difficult for these patients, according to the researchers.

“These findings support CO₂ hand baths as a safe, low-cost, non-pharmacological adjunct [treatment],” the scientists wrote, adding that “larger trials with clinical endpoints are warranted.”

Patients interested in trying the therapy should first consult their doctors, but a carbon dioxide hand bath might combine sodium bicarbonate (baking soda) and an acid (like citric acid or vinegar) in warm water. The fizzing reaction that results releases carbon dioxide, which can help boost circulation.

​The new study, “Carbon dioxide vs. warm-water hand baths in systemic sclerosis with secondary Raynaud’s syndrome – A capillaroscopy centered randomized controlled trial,” was published in the journal Microvascular Research.

SSc is an autoimmune disease characterized by the buildup of a protein called collagen, the main component of scar tissue. This leads to the accumulation of scar tissue in the skin and several internal organs, including the heart, kidneys, and lungs.

Nearly all people with SSC develop Raynaud’s phenomenon
Almost all SSc patients develop secondary Raynaud’s phenomenon, in which fingers and toes feel numb, prickly, and frigid in response to cold temperatures or stress. Raynaud’s is to due to excess collagen that narrows blood vessels.

Although pharmacological treatment may help ease these symptoms, many patients continue to experience frequent attacks and functional limitations. Thus, according to the researchers, “supportive non-pharmacological approaches are of particular interest.”

One such approach is CO2 baths, as the easy-to-use treatment has been shown to improve blood flow and oxygen supply to tissues. However, its effectiveness in SSc remains underexplored.

To learn more, the team conducted a clinical trial that assessed the effects of CO2 and warm water hand baths on blood flow in the fingers of 24 patients with SSc-associated Raynaud’s phenomenon.

The participants had a mean age in the late 50s and a disease duration of six years. All had abnormal nailfold capillaries, as assessed by nailfold capillaroscopy -- a noninvasive imaging technique that detects changes in blood flow of tiny vessels (capillaries).

Each was randomly assigned to receive a 15-minute hand bath enriched with CO2 (2 g/L at a constant temperature of 35  degrees Celsius, or 95 degrees Fahrenheit) or a warm water bath (at 40-42 degrees Celsius or 104 to 107.6 degrees Fahrenheit), which served as a control. Additionally, 12 healthy controls, age-matched to SSc patients when possible, received the CO2 hand baths.

Carbon dioxide hand baths shown to widen blood vessels
Before intervention, both SSc groups had higher capillary diameters than healthy participants, according to the team.

After intervention, CO2 hand baths resulted in significant diameter increases in the three capillary segments analyzed in both SSc patients and the controls. No such effects were seen with the warm water baths.

“The lack of response to warm water suggests impaired heat-induced vasodilation [blood vessel widening] in SSc, whereas CO₂ may engage alternative vasodilatory mechanisms,” the researchers wrote.

Relative to the healthy controls, the SSc patients showed a statistically significant increase in diameter immediately upon CO2 bath immersion in two of the segments. However, no such differences persisted at 10 minutes, though the blood vessel widening relative to warm water alone was still seen.

Further analyses indicated that capillary diameters declined after 10 minutes but remained higher than at the study’s start in patients and healthy participants who received CO2 baths. These results indicate that vasodilation partially persisted after the intervention, the scientists said.
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“Future research should explore repeated CO₂ applications, assess durability of effects, and integrate clinical outcomes in larger multicentre trials,” the researchers wrote. “Comparative studies with pharmacological vasodilators and other physical modalities would help define the role of CO₂ baths in comprehensive SSc –[Raynaud’s phenomenon] management.”