People forget, although they may realize perfectly the dangers of taking too much of a drug, that all forms of treatment can be carried to excess and have their dangers. This is especially likely to be true of treatments in which no sensation is felt during the period of treatment.
The x-ray, for instance, causes no sensation during the period of exposure but, as we now know, it is one of the most dangerous of all forms of energy unless properly controlled.
The same is true of sunlight and violet light therapy. The dangers of sunlight and violet light therapy are of various kinds. The simplest is what most patients who treat themselves learn sooner or later; that of severe burns on the skin of the body. The eyes should always be protected when taking ultraviolet light treatments. These treatments also should be begun very gradually and small, short exposures over a limited surface of the body should be given at first. This danger is perhaps most familiar in the case of the young man who has a short summer vacation and decides to get a good tan, all in one or two days. The result is that he usually spends most of the remainder of his vacation in bed.
Old people do not respond very well to light treatment, and their resistance to infections of all kinds is often greatly lowered by injudicious use of the method.
Tuberculosis of the lungs is the only form of tuberculosis which is definitely made worse by exposure to sunlight.
Skin diseases of many kinds are often made worse instead of better, by light. Especially is this true of acute skin diseases.
Damage to the heart muscle has been reported as the result of too long and too intense exposure to ultraviolet light.
All of this brings to mind the lesson that self-treatment is usually a very hazardous procedure. Especially dangerous is the doctrine that if a little of something is good for a thing, a great deal of it must be correspondingly better. Patients are often inclined to try to hurry the beneficial results by doing more than the doctor orders, and this is particularly likely to occur when a substance like light, which appears to be so innocent and so harmless, is being used.