PATHOGENESIS OF ALOPECIA 489 (c) Inectious (1) Localized. Superficial infection seldom causes permanent baldness. Deeper infection can cause temporary hair loss due to breakage of the hair shaft or direct involvement of the follicle. If the follicle is destroyed, scarring is produced and the alopecia is permanent. The following organisms may affect the follicle and cause alopecia viruses such as those of herpes simplex, zoster, varicella, variola bacterial infection such as tuberculosis, leprosy, and pyogenic organisms (Fig. 18). The follicles are also destroyed in oeolliculitis decalvans and ache varioliformis. Fungi usually cause temporary hair loss due to breakage of the involved hair 'z Figure 16.•40-year-old woman with hypopituitarism developed hair loss. shaft. Kerion may produce permanent hair loss, and certain fungi, such as favus, may destroy the follicles. (2) Systemic. Post-infec- tious alopecia usually fol- lows febrile episodes, with hair loss beginning about ten weeks after the onset. The following systemic in- fections are frequently as- sociated with hair loss: viral, such as influenza bacterial, such as typhoid (Figs. 19 and 20), scarlet fever, ery- sipelas, pneumonia trepo- nemal, such as syphilis yeast, such as moniliasis: and protozoa, such as ma- laria. (d) Neurologic an Psychiatric There is insufficient evidence that neurogenic factors influence the follicle directly. Trichotillomania refers to the subconscious or deliberate pulling out of the hair by the patient (Fig. 21). Scalp hair, eyebrows and occasionally eyelashes are the hairs most frequently attacked. This is frequently associated with trichokryptomania, the breaking off of the hair. A diagnostic aid is the painting of an affected patch with collodion or other occlusive material. Within a week the protected patch should show hair growth. Patients with this condition require psychiatric help. If tri- chotillomania is stopped soon enough .no permanent hair loss occurs.

490 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 17.--28-year-old woman with the adrenogenital syndrome. Figure 18.--Local bacterial f( lliculitis produced permanent hair loss.