Health Impact

Lanugo

Lanugo is a layer of fine, soft, downy hair. It is a normal part of fetal development in newborns — but when it appears on a teenager or adult, it is often the body’s attempt to stay warm in the face of severe malnutrition, and a recognized physical sign of anorexia nervosa.

A visible sign that the body has entered a starvation state

Written by the Eating Disorder Facts editorial team Awaiting clinical review by Cindy Hawthorn, MD Updated July 20, 2026

Key takeaways

Lanugo is fine, soft, usually unpigmented hair. It is normal in newborns but abnormal when it develops in older children, teens, or adults.
In malnutrition, the body grows lanugo to insulate itself and conserve heat after losing the body fat that normally keeps it warm.
It is a well-recognized physical sign of anorexia nervosa and severe malnutrition, and its extent can reflect how severe the malnutrition has become.
Lanugo itself is harmless, but it is a warning that the body is in a starvation state alongside more dangerous complications.
It is not treated directly — it resolves on its own as nutrition is restored and the body no longer needs the extra insulation.

Overview

What is lanugo?

Lanugo (pronounced la-NOO-go) is a coat of fine, thin, soft hair. Under normal circumstances it belongs to the earliest stage of human development, but it can also reappear later in life as a response to severe undernutrition.

When lanugo develops with malnutrition, it typically appears as fine, downy hair across the face, back, abdomen, chest, and forearms. It is distinct from the two other kinds of body hair: vellus hair (the short, faintly pigmented "peach fuzz" most people have) and terminal hair (the thicker, pigmented hair of the scalp, eyebrows, and body). Lanugo is softer, longer, and less pigmented than vellus hair — which is part of why clinicians can recognize it on a physical exam.

The normal context

Lanugo in newborns

Most people first grow lanugo before they are ever born. It develops on the fetus between roughly 16 and 20 weeks of pregnancy and helps hold protective vernix on the skin and support temperature regulation in the womb. It usually sheds in the last months of pregnancy, so many babies have shed it by birth — though premature infants, and some full-term newborns, may still have visible lanugo that falls out on its own within a few weeks.

In this context, lanugo is completely normal and requires no treatment. The concern arises when lanugo appears — or reappears — well beyond infancy.

The warning sign

Lanugo, anorexia, and malnutrition

When lanugo develops in an older child, adolescent, or adult, it is almost always a signal that something is wrong. Most often, it reflects significant weight loss and malnutrition, and it is one of the classic physical signs of anorexia nervosa. It can also appear in other states of severe undernutrition.

Clinicians pay attention to both the presence and the extent of lanugo, because its distribution can correlate with how severe the malnutrition has become. The growth of lanugo can also serve as a marker of treatment response — as nutrition is restored, the fine hair tends to recede, tracking improvement in the person’s overall physical health.

The mechanism

Why the body grows lanugo

Losing the body’s insulation

Body fat is a major part of how humans stay warm. In severe malnutrition, the loss of fat and muscle strips away that insulation, core temperature drops, and people become vulnerable to feeling cold constantly and to hypothermia. Growing a layer of fine hair is one of the body’s adaptive attempts to trap heat and insulate itself — a survival response to starvation.

Hormonal drivers

Starvation also disrupts the body’s hormones in ways that promote lanugo growth. In anorexia nervosa, levels of the active thyroid hormone T3 fall (a pattern resembling "euthyroid sick syndrome"), and the growth factor IGF-1 is reduced, while the stress hormone cortisol is frequently elevated. Together these hormonal shifts help drive the growth of fine lanugo hair.

Why it matters

What lanugo signals about health

On its own, lanugo is harmless — it does not hurt and causes no direct medical danger. Its importance is what it represents: the body has entered a starvation state serious enough to change how it grows hair to survive.

That state rarely occurs in isolation. Lanugo commonly appears alongside other complications of malnutrition, such as a slowed heart rate, low blood pressure, feeling cold, brittle hair and nails, loss of menstrual periods, and bone density loss. It can also signal that a person is at risk during nutritional restoration — see our guide to refeeding syndrome. For that reason, new lanugo growth should prompt a medical evaluation rather than reassurance.

Recovery

Does lanugo go away?

Yes. Lanugo is not treated directly — there is no cream or procedure aimed at the hair itself. Instead, it resolves as the underlying malnutrition is corrected. As a person renourishes, restores body fat, and regains the ability to regulate temperature, the body no longer needs the extra insulation, and the fine hair gradually sheds and stops regrowing.

The timeline is individual and follows the pace of physical recovery rather than a fixed schedule. Trying to remove lanugo cosmetically misses the point: the meaningful step is treating the eating disorder or malnutrition that caused it. As health returns, the lanugo goes with it.

Next steps

When to seek help

If you or someone you love has developed fine, downy hair on the face, back, or arms along with weight loss, food restriction, feeling cold all the time, or other changes, treat it as a signal worth acting on. Lanugo in a teen or adult is a reason to seek a medical assessment for an eating disorder or other cause of malnutrition.

Learn more about the warning signs of eating disorders and how to find specialized help. Recovery restores not only the body’s warmth and health, but usually clears the lanugo along the way.

There is hope

Lanugo is the body asking for help.

If fine hair growth appears alongside weight loss or food restriction, a specialized team can assess what is happening and guide recovery.

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