Some vegetarians, people who go on crash diets that exclude protein, and those with severely abnormal eating habits, may develop protein malnutrition. When this happens, a person's body will help to save protein by shifting growing hairs into the resting phase. Massive hair shedding can occur two to three months later. Hair can then be pulled out by the roots fairly easily. This condition can be reversed and prevented by eating the proper amount of protein and, when dieting, maintaining adequate protein intake.
Prescription drugs cause temporary hair shedding in a small percentage of people.
Certain types of drugs for treating cancer will cause hair cells to stop dividing. Hair shafts become thin and break off as they exit the scalp. This can occur one to three weeks after the cancer treatment. The patient may lose up to 90 percent of this or her scalp hair. The hair will regrow after treatment ends.