This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The good effects already described as proper to sea-bathing may be missed, and very unpleasant symptoms may arise, if attention be not given to certain points.
The therapeutical object is to secure and sustain a good reaction, and this is impaired if the bath be too cold, or too prolonged, or if excessive exertion be taken before, during, or after it, or if the patient be under the influence of strong emotion, as a nervous, frightened child would be. The most common errors are to prolong the bath unduly and to exert one's self overmuch during it: the sense of vigor is then replaced by exhaustion, the skin again becomes cold, and the circulation depressed; giddiness and headache occur from altered conditions of the circulation, with general malaise, and possibly shivering, nausea, sickness, and a sense of depression lasting for many hours. It is therefore important to leave the bath before the stage of reaction and stimulation is finished. With some persons the stroke of three or four good waves is sufficient for the best results, five minutes is an average time for the delicate to remain in the water, and no one bathing for health only should remain in the open sea for more than ten minutes.
At the extremes of life, sea-bathing in the open should be practised cautiously. As a rule, it is unsuited for children under two years of age, or for patients over sixty. Pregnancy in healthy subjects need not prevent the use of salt-baths, or sea-bathing, provided that the patient is accustomed to a cold-bath previously, but as a rule, the various inconveniences of open-air bathing render its risks greater than any advantage in that state. The tendency to cause congestion, more or less temporary, of internal organs, the brain, liver, lung, or kidney, renders open-air sea-bathing unsuitable for persons disposed to such disorders, or suffering from structural change or marked blood-stasis within the abdominal organs, albuminuria, serious cardiac disease, chronic pneumonic infiltrations, haemoptysis, fatty degeneration, or rheumatism which is at all acute. An extreme degree of anaemia is a contra-indica-tion.