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March 13, 1967

Diagnosis With Wood's Light: Tinea Capitis and Erythrasma

Author Affiliations

From the Division of Dermatology, University of Oregon Medical School, Portland.

JAMA. 1967;199(11):841. doi:10.1001/jama.1967.03120110113021

For less than $100 any one can own a Wood's light; yet this diagnostic tool is not standard equipment in the physician's office. A Wood's light produces long-wave ultraviolet light with a maximum at a wavelength of 3,600 Angstrom units (by comparison, the sunburn range is 2,800 to 3,200 A, and visible light is greater than 4,000 A). Some chemical substances which absorb long-wave ultraviolet light will be excited by this lamp to emit light of a longer (visible) wavelength. When viewed under a Wood's light in a dark room, the substance will appear to have a characteristic color depending upon the wavelength of the emitted (fluorescent) light. The use of this fluorescence in the office diagnosis of several diseases will be discussed in this and the succeeding communication.

The examination of the scalp of children for the presence of ringworm (tinea capitis) with the Wood's light is a simple,