Promethazine-HCl was used to suppress histamine production in the skin by Na₂SO₄·NaHCO₃ bathing, confirming the previous data that the small amount of histamine released as a chemical mediator may have caused the warming effect, as observed in type I allergic reaction.
The skin histamine contents after serial bathings with Na₂SO₄·NaHCO₃ under medication of Promethazine-HCl for 3 weeks were significantly reduced compared with that of tap water (p<0.05).
The skin histamine produced by physical stimulation of Na₂SO₄·NaHCO₃ bathing was suppressed with H₁-blocker (Promethazine), verifying that the warming effect with Na₂SO₄·NaHCO₃ bathing was caused by histamine released as a chemical mediator, as observed in type I allergic reaction.

The warming effect of alkaline saline springs is thought to be caused by the presence of Na₂SO₄·NaHCO₃. To clarify the warming effect of alkaline saline springs, an experimental study was carried out using 5 adult rabbits for each 36-37°C bath every day for 20 minutes without anesthesia, on the assumption that cells in the skin tissue were activated to produce histamine by chemical stimulation. The chemical composition of each artificial salt bath was 4 times higher than normal. Skin histamine was measured by fluorescence analysis.
Single bathing in each artificial salt bath had no significant effect on the skin histamine contents. However, the skin histamine contents after a serial bathing in Na₂SO₄·NaHCO₃ (p<0.01) and CO₂ baths (p<0.05) for 3 weeks were significantly increased compared with that of tap water.
The small amount of histamine released as a chemical mediator may have caused the warming effect, as observed in type 1 allergic reaction.

The warming effect following serial bathing in the water containing Na₂SO₄·NaHCO₃ was studied in rabbits by mass spectrometry.
Rabbits, weighing about 2kg, were placed in a bath containing Na₂SO₄·NaHCO₃ (33g/20l) at 36-37°C for 20 minutes every day for 3 weeks.
By mass spectrometry, the subcutaneous tissue perfusion rate was calculated on the basis of changes in the partial pressure of Argon injected on diffusion membrane of the sensor catheter.
The mean subcutaneous pCO₂ was 46.6±14.6mmHg in the Na₂SO₄·NaHCO₃ bath group and 28.8±6.7mmHg in the control tap water group; the tissue perfusion rate in these two groups was 26.78±6.45ml/100g/min and 20.32±7.15ml/100g/min, respectively.
The warming effect of Na₂SO₄·NaHCO₃ bathing is thought to be derived from increased metabolism and micro-circulation dynamics resulting from dermal stimulation by Na₂SO₄·NaHCO₃.

We previously found experimentally that the subcutaneous tissue perfusion rate was increased by about 16% upon inhalation of high concentration radon (13, 764-23, 743Bq/l).
To clarify the effect of a lower concentration of radon water by mass spectrometry, the subcutaneous tissue perfusion rate was determined experimentally in rabbits using fourth-day radon water of a 3, 519-6, 710Bq/l concentration taken from a mineral spring.
The subcutaneous tissue perfusion rate with inhalation of the radon water was 15.81±3.10ml/100g/min (mean±SD, n=10), which was similar to that with inhalation with physiological saline solution (15.96±3.09ml/1008/min, n=16). However, the subcutaneous tissue perfusion rate with inhalation of more highly concentrated, first-day, radon water (8, 641-17, 366Bq/l) was 20.76±3.58ml/100g/min (n=16), being significantly higher (p<0.01) than that with water at lower radon concentration.
Further studies are needed on the effect of radon water in relation to the hormesis with low dose of radiation.

The effect of bathing with carbonated (CO₂) water by condensing direct heat exchange type heater (CONDEC, Osaka Gas, Co., Ltd.) on tissue perfusion in rabbits was evaluated experimentally by means of mass spectrometry.
CONDEC supplies CO₂ water at 100-150ppm at 40-60°C by a latent heat collecting system in which the combustion gas directly contacts the running water.
Mean pH of the water in the bath decreased 15%, mean pH of the subcutaneous tissue decreased 1%, and mean pO₂ and pCO₂ in the subcutaneous tissue increased 7% in comparison to values obtained when tap water was used.
Mean tissue prefusion rate was calculated to be 21.71±2.34ml/100g/min (n=11, p<0.05), 15% higer than obtained when tap water was used (18.81±2.96, n=9).
CONDEC CO₂ water is thought to be useful for hydrotherapy and for application in health promoting facilities in promoting the tissue perfusion, which is known to lead to recovery from fatigue and chronic pain.