Ms. Huffman had assumed that the skin-picking behavior was unique to her. It never occurred to her to seek treatment.

In fact, it’s relatively common. So, too, are a family of related habitual behaviors that include hair pulling, nail biting and cheek biting, among others. While there’s no easy fix, they can typically be treated in a psychotherapy setting by a clinician trained in habit-reversal therapy and other behavioral-therapy methods.

Yet we hear little about these conditions, which makes them more difficult to identify, treat and study. The intense shame that affected individuals experience is a contributing factor.

Nearly everyone picks at the occasional scab or plucks a stray hair now and then. But mental-health professionals make a distinction between those normal grooming acts and a habit that an individual is unable to curb despite attempts to do so, or which causes distress. Habits that meet these criteria are known collectively as body-focused repetitive behaviors. Some patients engage in more than one behavior.

Habitual skin picking is formally called excoriation disorder (in the past, it was known as dermatillomania). It affects roughly 1.4 percent of the population, according to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (D.S.M.-5). (Some studies put the rate higher.) Hair pulling, or trichotillomania, occurs in about 0.5 to 2 percent of people, according to the same manual. The behaviors are classified in the chapter covering obsessive-compulsive and related disorders. This edition, published in 2013, was the first in which the American Psychiatric Association included detailed information about skin picking.