Opinions are divided as to the benefits or otherwise of cold baths and showers, but at the turn of the 19th Century Dr Samuel Solomon thought he had it cracked, and offered some detailed and definitive advice in the American health book A Guide to Health, published in 1803. The book concludes with a lengthy article about cold bathing. Here are some choice quotes:
The cold bath recommends itself in a variety of cases ; and is peculiarly beneficial to the inhabitants of populous cities, who indulge in voluptuousness, and lead sedentary lives. In persons of this description the action of the solids is always too weak, which induces a languid circulation, a crude indigested mass of humours, and obstruction in the capillary vessels and glandular system. Cold water, from its gravity as well as its tonic power, is well calculated either to obviate or remove these symptoms. It accelerates the motion of the blood, promotes the different secretions, and gives permanent vigour to the solids. These important purposes are always most essentially answered by sea-bathing; for salt water ought to be preferred, not only on account of its superior gravity, but likewise for its greater power of stimulating the skin, which promotes the perspiration, and prevents the patient from catching cold….
Very fat or corpulent persons should avoid the cold bath, for their fibres are so stuffed round, and as it were bolstered up, that they have no room to vibrate or contract, with the sudden squeeze of the bath; instead therefore of enforcing their springs and shaking off any unnecessary incumbrances, they will only be strained to no purpose, and consequently weakened; for wheresoever an effort is made to remove any thing by an elastic body, if the first exertion fails, every impetus afterwards languishes, and the spring is spoiled….
Another class of patients who stand peculiarly in need of the bracing qualities of cold water, is the nervous. This includes a greater number of the male, and almost all the female inhabitants of great cities. Yet even these persons ought to be cautious in using the cold bath. Nervous people have often weak bowels, and may, as well as others, be subject to congestions and obstructions of the viscera; and in this case they will not be able to bear the effects of the cold water….
The most proper time of day for bathing is, no doubt, the morning, or at least before dinner; and the best mode that of quick immersion. As cold bathing has a constant tendency to propel the blood and other humours towards the head, it ought to be a rule always to wet that part first, or as soon as possible.
So there we have it. Readers of A Guide to Health in 1803 would have been left in no doubt as to the virtues of cold water for all the nervous city folk and the dangers for the corpulent. But it was all fine as long as you plunged in head first.