Phototherapy
Collier's New Encyclopedia (1921)
the application of light rays to the treatment of such diseases as tubercular glands, eczema, cancerous growths, lupus epithelioma, and acme vulgaris. In the decomposition of sunlight or artificial white light, it has been found that different rays have different qualities, some being calorific, or heat-producing, others producing light without heat. Experimentation has proved that there are rays beyond both extremes of the visible spectrum, called ultra rays. The ultra-red rays produce greater heat than the red ray, which is the extreme visible heat calorific ray. The violet rays and ultra-violet rays are known to be bactericidal, since culture of bacteria which have been exposed to their action are killed. These rays produce an inflammation (sunburn) and have the power of penetrating the skin. Dr. Niles R. Fensen, of Copenhagen, Denmark, who introduced this work to the medical profession in 1892, is acknowledged to be the pioneer in the use of light rays for curative purposes. Since it is necessary to use some sort of filtering lens in order that the heat rays do not act upon the part to be treated, Dr. Fensen used an apparatus consisting of double quartz lenses, between which was placed an ammoniacal solution of sulphate of copper. This solution is opaque to the ultro-red, red, orange, and yellow heat rays, but transparent to the blue, violet and ultra-violet light rays. White light must first be broken up into its component colors, and the heat rays removed by filtering, after which they are focused on the surface to be treated. In spite of the filter, artificial cooling of the surface undergoing treatment is sometimes necessary. The electric bath cabinet was invented by Kellog in 1894. In this case the patient is placed in a cabinet with his head projecting through an opening in the top, and his body subjected to a baking process, the heat being furnished by various lights inside the cabinet which are controlled by an attendant. This treatment is used for rheumatism, obesity, and for internal congestion. In responsible hands there is no doubt that much benefit is derived by the practice of these methods, and there are many reputable sanitariums and practitioners of phototherapy, but it has also given rise to many drugless health resorts and other questionable institutions whose object is to prey upon the helpless and infirm.
What Has Changed in the Last Century
Collier's spelling slips "Dr. Niles R. Fensen" is Niels Ryberg Finsen, who won the 1903 Nobel Prize in Medicine for the very lamp described here; his treatment of skin tuberculosis (lupus vulgaris) was superseded in the 1940s and 50s by antibiotic drugs, and the Finsen lamp with its copper-sulphate filter is now a museum piece. Phototherapy itself did not die but changed patients: the commonest use today is blue light for jaundice in newborns, an effect noticed in a British hospital nursery in the 1950s and unknown in 1921, while narrow-band ultraviolet B and psoralen-plus-UVA are standard for psoriasis, eczema and vitiligo. Light is still used against cancer, but as photodynamic therapy, in which a drug given beforehand makes the tumour sensitive to a laser or lamp, rather than by burning the growth as the older accounts imply. Two things Collier's could not have said: ultraviolet light is now known to cause skin cancer as well as treat disease, so dosing is carefully limited; and the "electric bath cabinet" of Kellogg, offered here for rheumatism and obesity, has no place in modern medicine, though bright-light boxes are prescribed for seasonal depression.
Written for this edition, 2026.