Lanugo is fine, soft, downy hair that grows on the body when someone with anorexia nervosa becomes severely malnourished. It typically appears on the sides of the face, along the spine, and on the arms and legs. While lanugo is normal on fetuses in the womb (most babies shed it before birth), its reappearance in adolescents or adults is a visible sign that the body is struggling to keep itself warm.
Why the Body Grows Lanugo
As anorexia progresses, the body loses subcutaneous fat, the layer just beneath the skin that normally acts as insulation. Without that fat layer, core body temperature drops, and the body loses its ability to regulate heat effectively. Hypothermia is a well-documented complication of anorexia nervosa.
Lanugo is the body’s attempt to compensate. When temperature sensors in the skin detect that heat regulation has gone wrong, they trigger signals in the hair follicles that reactivate the growth of this primitive, downy hair. The hair creates a thin layer of insulation over the skin’s surface, trapping a small amount of warm air close to the body. It is not a cosmetic change or a hormonal side effect. It is a survival mechanism, one that kicks in when the body has exhausted more conventional ways of staying warm.
What Lanugo Looks and Feels Like
Lanugo hair is distinctly different from normal body hair. It is very fine, soft, and usually unpigmented or lightly colored, sometimes described as peach fuzz. It does not grow thick or coarse. The clinical term for this widespread hair growth is diffuse hypertrichosis, meaning excess hair spread broadly across the body rather than concentrated in one area.
The most common locations are the sides of the face (especially along the jawline and cheeks), the back and spine, and the arms and legs. It can be subtle enough that someone might not notice it immediately, or it can become quite visible, particularly on the face and back. In children and adolescents with anorexia, extensive lanugo hair is considered one of the distinctive dermatologic findings.
Other Symptoms That Appear Alongside Lanugo
Lanugo rarely shows up in isolation. By the time the body resorts to growing insulating hair, other signs of serious malnutrition are typically present. These tend to cluster together because they share a common cause: the body is running out of energy and shutting down nonessential functions to protect vital organs.
Cold intolerance is one of the most closely related symptoms. People with anorexia often feel cold even in warm environments, and their fingers, toes, nose, and ears may develop a bluish discoloration called acrocyanosis. This happens because the body redirects blood flow away from the extremities and toward the core to preserve heat, the same temperature crisis that triggers lanugo growth.
Heart rate slows significantly. Bradycardia, a resting pulse below 60 beats per minute, occurs in up to 95% of people with anorexia nervosa. Blood pressure drops as well. These cardiovascular changes, combined with hypothermia, represent some of the most dangerous physical consequences of the disorder. Lanugo, while not dangerous on its own, is a visible indicator that these internal changes are likely happening too.
What Lanugo Means as a Clinical Sign
For clinicians, the presence of lanugo is a red flag that malnutrition has reached a point where the body’s thermoregulation system is failing. It is regularly noted in physical exams of people with anorexia nervosa and is one of several skin-related findings (along with dry skin, hair thinning on the scalp, and brittle nails) that point to nutritional deficiency.
Lanugo is not unique to anorexia. Any condition that causes severe malnutrition can trigger it, including other eating disorders, malabsorption syndromes, or extreme caloric restriction for any reason. However, in practice, it is most strongly associated with anorexia nervosa because of the prolonged, severe energy deficit the disorder creates.
Does Lanugo Go Away With Recovery?
Lanugo is reversible. Because the hair growth is driven by the body’s response to heat loss from malnutrition, restoring adequate nutrition and body fat removes the trigger. As weight is restored and the body regains its ability to regulate temperature normally, the signals that stimulated lanugo growth stop, and the hair gradually sheds on its own.
There is no need to shave or remove lanugo. It falls out naturally as the underlying condition improves. The timeline varies from person to person and depends on how quickly nutritional rehabilitation progresses and how much body fat is regained. For most people, the hair becomes noticeably less prominent within weeks to months of sustained weight restoration. Its disappearance is often taken as one visible marker that recovery is moving in the right direction, just as its appearance was a marker that things had become medically serious.