That too much exposure to the sun's rays may be not beneficial, but distinctly deleterious, has been asserted by various writers on the subject. At this season it may be relevant to call attention to a custom that is said to prevail in certain parts of Germany of lying naked for hours on the bank of some stream, entering the water from time to time, and then returning to the bank to lie in the sun, the purpose being to obtain therapeutic benefit from the sunlight by this return to nature.
SUN-BATHS AND COMMON SENSE. JAMA. 2010;304(6):695. doi:10.1001/jama.2010.1041