A marked loss of hair takes place after infectious diseases, such as typhoid fever, influenza, diphtheria, syphilis, etc. This represents a troublesome form of affection, a true weakening of the scalp ; and the deficiency of hair-formation leads to complete bald ness (see Fig. 206). It is beyond question that predisposition (heredity) as well as acquired injuries are factors in causing this affection which, probably on account of an erroneous belief in the possibility of losing the hair in consequence of excessive enjoyment, oft en causes the afflicted indvidual to become the target for sar casm and raillery. However, the mode of living has but a very limited influence upon the loss of hair, and only in so far as it is fraught with special dangers. Youthful dissipations and early baldness have very little relation to one another. The loss of hair often occurs in almost regular circular or oval spots (see Fig.
207). The cause of this phenomenon is not fully explained as yet ; either nervous influences or the action of fungi arc held responsible. Treatment consists in the application of stimulating or disinfecting remedies, such as tar in the form of soap or mixed with the yolk of an egg. If mental exertions are held responsible for the loss of hair, other symptoms affecting the general health should be sought for. Pressure of the hat-rim is likewise often wrongfully regarded as the cause of circumscribed baldness. It is possible that continued pressure may diminish the blood supply to the scalp, and thus cut off the nourishment of the hair follicles. In such a case it is advisable to invigorate them by frequent massage (combing) and by washing with the yolks of eggs. The various remedies so exten sively advertised are not likely to accomplish more than massage combined • with the application of tar and egg-yolks.
HAIR-DYES.--The modern art of dyeing the hair has advanced so far that it is able to comply with the taste (or lack of it) of everyone who is prompted by the singular desire to improve upon Nature by changing the colour of his hair. Caution should be given against such a step into the dark unknown. The majority of those who have had their hair dyed
have been thoroughly dissatisfied with the result. Since the proper dyeing of the hair requires a thorough knowledge of the properties of the dye employed, the experiment should never he undertaken without the aid of 'an experienced hairdresser. Harmless hair-dyes do not exist.
To prevent the hair from turning grey, frequent washing with the yolk of eggs can be recommended. The oil of eggs is an old Roman device for preserving the hair. Neat's-foot oil has also been highly and justly recommended as a means of darkening the hair.
Hair-dyes in pomades act very slowly, and must be used daily until the desired results have been attained. Those prepared from vegetable ingredients are in general to be preferred to those containing metallic substances. Walnut shells and green walnuts dye blonde or grey hair first yellowish, then dark-brown ; but the colour is not durable. Nut pomade is of no use whatever. The action of nut extract is due to its contents of iron chloride, pyrogallic acid, copper chloride, and free hydrochloric acid. Powder made from the leaves of the henna-bush and the indigo-plant in correct mixtures (which may be determined by experimenting with bristles) will give shades of yellow, orange, brown, and deep black. Brown coal (lignite), with ammonia, potash, and peat-water--a mixture known as " Nerin "—is also used for dark shades. Kohol is India ink with gum dis solved in rose water ; mixed with silver salts, verdigris, iron tatmate, lead carbonate and other mineral substances, it gives dark shades.
Blonde shades (in great favour among certain lower classes) are acquired by washing the hair with hydrogen peroxide. Dyes that contain lead (and these are by no means few) are particularly dangerous, often leading to lead-poisoning. Before applying the dye, the hair should be freed of all fatty matter by the application of a mixture of twenty parts of chloroform with eighty parts of alcohol. The dye is applied with a comb and a new toothbrush, and the hands should he protected by gloves.