As in the case of other life elements, man cannot do without sunlight. The sun is the source of light and heat. If there was no sun, there would be neither light nor warmth. Unfortunately, we do not make full use of sunlight and consequently we are unable to enjoy perfect health.
Sunbath is as useful as ordinary water bath though the two cannot replace one another. In cases of delibity and slow circulation, exposure of the uncovered body to the morning sun acts as an all-round general tonic and accelerates the metabolism.
The morning sun has the largest amount of ultra-violet rays which are a most effective component of the sun's rays. If the patient feels cold, he should lie in the sun covered up and gradually expose more and more of his body as he gets used to it.
One can also take the sunbath pacing up and down in the sun without any clothes on, in a private enclosure or in any other place away from public gaze. If such a place is not within easy reach, one can just cover up the private parts by tying up a piece of cloth or a langoti and expose the rest of his body to the sun.
I know of many persons who have been benefited by sunbaths. It is a well-known treatement for tubercolusis. Sunbaths or heliotherapy is no longer confined to the sphere of naturopathy. Orthodox medicine has taken it up from naturopathy and developed it further. In cold countries, special glass buildings have been constructed under medical supervision, so that the glass lets in the sun' rays and at the same time protects patients against the cold.
Sun treatment often results in the cure of intractable ulcers. To produce sweating, I have made patients lie in the sun at about 11 a. m., i. e. a little before midday. The experiment has been successful and the patients are soon bathed in sweat. In these cases the head should be protected from the sun by means of a cold mud poultice. Banana or any other leaves can be used to cover up the head and the face and thus further help in keeping the head cool and well protected. The head should never be exposed to strong sunlight.
Source: Key to Health (M. K. Gandhi).