It has been widely recognized that the drinking of strongly acid hot spring water often causes gastrointestinal symptoms. However, the research in this subject has been distinctly sporadic.
Fundamental and clinical experiments were undertaken to ascertain the effect of the drinking of Tamagawa Spa on the gastrointestinal mucosa. The property of Tamagawa Spa, Akita prefecture, is acid vitriol spring whose pH value is 1.2, and it contains a large amount of hydrochloric acid and hydrogen sulfide.
1. Studies in Man
The changes of gastric mucosa in 36 subjects after the drinking of hot spring water were observed by gastrocamera or gastrofiberscope.
Varying degrees of hyperaemia were found in all subjects administered non-diluted hot spring water, whereas these change were markedly reduced in subjects administered two times and over diluted hot spring water.
No instances of erosion or ulceration were seen in any of the subjects.
2. Experiments in Animals
Twenty three healthy rabbits, orally administered non-diluted or diluted hot spring water for seven days were autopsied.
The changes of gastric mucosa were similar to those in man, and no significant influence on the jejunal mucosa was seen. Microscopically the affected mucosa revealed degeneration of the epithelial cells of gastric gland and edema of the submucosa.
Based on the critical review of former studies, several important factors were suggested to explain the occurrence of gastric impairment after the drinking of Tamagawa Spa water.

The results obtained from a survey of balneal treatment and medical researches made at Hanezawa Spa in Yamagata Prefecture are summarized as follows.
1) Visitors to this spa vary in age, include both sexes in equal number and are, by far, farmers.
2) Visitors are mostly from the local area and surrounding villages and towns, 70% of whom come to the spa for recreation and 20% for therapeutic treatment and recuperation. The figures mentioned here greatly depend upon the time this survey was made, and it is quite probable that the number of visitors for balneal treatment should always be much larger.
3) In this survey, short-time visitors are largest in number, coming to the spa for recreation. Long-time visitors come there for balneal treatment. Visitors are mostly those with diseases of the digestive organs and those with the skin diseases.
4) The larger number of visitors bathe four to five times a day and about 40% of them drink hot-spring waters. Because of the presence of a large number of short-time visitors, the effect of balneal treatment and bathing reaction could not be made clear.
5) Only 4.4% of visitors came there under doctor's directions.
6) Observation of the effect of drinking hot-spring waters on the excretion of gastric juice revealed that it has power to neutralize acid in the stomach and to control the excretion of gastic juice. Such should naturally be the case because this spa is of alkaline muriated spring.
7) With a view to find the effect of drinking hot-spring waters at this spa, examinations were made of renal function. The results obtained from the dilution tests show that the urinary excretion has been delayed and the power of dilution has declined. It is advisable, therefore, that visitors should see whether they are afflicted with the diseases of kidney or circulatory system before they resort to drinking hot-spring waters at this spa.

Our overall surveys of medical consultations for balneal therapy and of balneal curation at the Namekawa Spa, Yamagata Prefecture may be summarized as follows.
1) The Namekawa Spa is one in the Iegatayama Spa family located in the border of Fukushima and Yamagata Prefecture, which is saline hydrogen sulphide spring in character.
There is only one hot-spring inn in this resort (Fukushimaya Inn). It is rich in natural scenery, without the atmosphere of an amusements center and isolated from the wordly things. It is purely a spa for balneal treatment.
2) The larger number of visitors to this spa are from within the prefecture, especially from the towns and villages around the spa, but, because of its nearness to Fukushima Prefecture, quite a number of visitors are from this prefecture.
The visitors are mostly farmers, especially those of advanced age.
Half the visitors have been at the spa before and many of them are in the habit of revisiting the spa year after year.
3) A majority of visitors come to the spa for therapy of diseases and for recuperation, which shows that this spa has the character of balneal therapy.