Like the skin and its appendages, the teeth, nails and hair, so also other tissues of ectodermal origin are here shown to be affected by fluorine. The action of fluorine consists in lowering the level of the calcium in the blood and tissues. The epithelia of the mouth and the salivary glands, of the nasopharynx, the conjunctivae and the lachrymal glands may be affected. Signs and symptoms are thus produced which are closely similar to those usually attributed primarily to infection. It is suggested that an infection accompanying chronic fluorine poisoning is of a secondary nature, and that it is brought about by the loss of calcium in the body.

The modern study of the problem of fluorosis (chronic fluorine poisoning) became possible when an Italian, Stefano Chiaie, described, as quoted by Eager (1901), an unsightly dental dystrophy, now known as ‘mottled teeth’. The efforts to trace its aetiology have been ceaselessly continued ever since, mainly by American investigators. Outstanding amongst these were Black & McKay (1916), pioneers whose researches led to the discovery made by Smith, Lantz & Smith (1931) that it was the fluorine, contained in drinking water, in a concentration of not less than 1 part per million (1 p.p.m.) and ingested during the period of calcification of the teeth, which was the direct cause of the dental dystrophy. This result was soon followed up by a number of observers, mainly in the United States under the leadership of the dental profession, amongst them physiologists, experimental pathologists, pharmacologists, veterinary surgeons, geologists and analytical chemists. The gate for further research, which in view of its magnitude and importance must be considered as being still in its infancy, has thus been thrown wide open.

A high proportion of young men in this country suffer from premature baldness. Alopecia is not a disease entity but one of the outstanding features of chronic fluorine poisoning (fluorosis). It is frequently associated with dystrophies of other organs of ectodermal origin, namely, those of the skin and its other appendages, the teeth and nails. Since all these organs are regulated by the parathyroid glands, it is concluded that alopecia, too, is produced by fluorine acting through the medium of these endocrine glands. By its ability to precipitate the calcium content of the body, fluorine may lay the foundation for alopecia already in intra-uterine life, or produce it at any time after birth.The action of fluorine is closely similar to that of thallium. There is ample evidence to show that in both fluorosis and chronic thallium poisoning the vegetative nervous system is vitally involved.Toxic alopecia due. to fluorine is preventable.

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Dystrophies due to chronic fluorine poisoning in organs regulated by the parathyroid glands, namely the skin and its appendages, the nails, teeth and hair, and also in bones, are here shown to be unusually common in this country. They should be regarded as easily detectable signs of a serious disturbance of the calcium metabolism of the body. Fluorine is a poison of which the action, in many respects, is similar to that of arsenic. It is the task of the authorities responsible for the health of the nation to search for ways and means capable of minimizing its effect.I wish to express my sincere thanks to the Librarian of the Royal Society of Medicine and his staff for their never-failing courtesy and help.