Lanugo: The Protective Fine Hair of Fetal Development
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Lanugo is a specialized type of fine, soft hair that develops on a fetus between 16 and 20 weeks of pregnancy. Its primary roles are to provide warmth, anchor protective vernix to the skin, and stimulate fetal growth through sensory vibrations. While most babies shed this hair before birth, it is common in premature infants and typically disappears within two months. In adults, however, the appearance of lanugo can be a significant indicator of malnutrition, eating disorders, or certain rare tumors [1].
Quick Answer: What is lanugo?
Lanugo is the first hair produced by fetal hair follicles, forming a protective layer during development in the uterus. It helps regulate temperature and holds vernix in place to protect skin from amniotic fluid. Most fetuses shed it in the final eight weeks of pregnancy. In older children and adults, lanugo is often linked to severe weight loss and malnutrition. [1]
What the research says
Widespread excess body hair (diffuse hypertrichosis) is a recognized skin sign of anorexia nervosa. In a clinical study of 24 consecutive patients with anorexia nervosa, diffuse hypertrichosis was seen in 25% and was more common in the restrictive type; in the two patients followed for 3 years, it appeared not to be linked to changes in body mass index (Strumìa et al., Dermatology, 2001 [2]).
Lanugo-type hair appearing in an adult can be a sign of internal cancer. A review of acquired hypertrichosis lanuginosa reported it in 56 patients as a paraneoplastic syndrome, mostly aged 40 to 70; the most frequent associated cancer was colorectal in women and lung in men, and in the authors' 10 patients the cancer had usually already metastasized. The authors stress that lanugo-type hair in areas a patient saw as previously hairless is highly indicative of internal malignancy (Slee et al., Br J Dermatol, 2007 [3]).
What Is Lanugo?
Lanugo is a soft, thin, and feathery hair that covers a fetus during its development in the uterus. It is distinct from the hair adults have on their heads or bodies. This fine "fur-like" coating is a natural part of the human growth cycle, appearing mid-pregnancy and typically shedding as the fetus prepares for birth [1].
Timeline of Lanugo Development
Lanugo follows a specific biological schedule, transitioning into other hair types as a child grows [1].
Stage | Timing | Description |
|---|---|---|
Development | 16–20 Weeks | Lanugo begins to grow across the fetal body. |
Shedding | Last 8 Weeks | Most lanugo falls off and is replaced by vellus hair. |
Newborn Phase | Birth–2 Months | Any remaining lanugo typically disappears on its own. |
Lanugo grows from weeks 16 to 20 of pregnancy, sheds in the last eight weeks, and may still be visible on a newborn's back and shoulders, especially in premature babies.
What are the main functions of lanugo?
Lanugo is not merely decorative; it serves three essential purposes for a developing fetus [1]:
Skin Protection: It helps the waxy vernix substance stick to the skin, protecting delicate skin from constant exposure to amniotic fluid.
Temperature Regulation: It provides insulation, keeping the fetus warm until it develops enough body fat to regulate its own temperature.
Growth Stimulation: Movement of the lanugo hairs sends vibrations to sensory receptors, which stimulate fetal growth.
Lanugo hairs hold the protective vernix against the skin, insulate the fetus, and send sensory signals that stimulate growth.
Why does lanugo appear in adults, and what conditions cause it?
While lanugo is a healthy sign in infants, its appearance in children, teens, or adults is often a warning sign of an underlying health issue [1].
Eating Disorders and Malnutrition
In conditions like anorexia nervosa or bulimia, the body may lose so much fat that it can no longer keep itself warm. Healthcare providers believe the body grows lanugo in response, to provide extra insulation and help conserve heat. Lanugo can indicate poor nutrition and malnourishment [1].
Tumors and Cancer
In rare cases, the growth of lanugo in an adult can be linked to teratomas (germ cell tumors) or certain types of cancer. If an adult notices fine, feathery hair growth, it is essential to consult a healthcare provider to rule out these serious conditions [1].
How is lanugo cared for and managed?
The approach to managing lanugo depends entirely on the age of the individual and the cause of the hair growth [1].
For Newborns: No treatment is necessary. Parents should avoid waxing, shaving, or using hair removal creams, as a baby's skin is extremely sensitive. The hair will fall off naturally within weeks.
For Adults: Treatment focuses on the underlying cause. Getting help for an eating disorder or malnutrition, or removing a tumor, is the first step, and the lanugo should stop growing once the cause is treated. Shaving or waxing may be an option, but the hair will keep growing back until the underlying condition is treated.
In newborns lanugo disappears on its own and should not be shaved; in adults it is a reason to seek medical advice.
What is the bottom line on lanugo?
Lanugo is a fascinating biological tool that ensures a fetus remains protected and stimulated during its most vulnerable stages of development. While its presence at birth can be surprising to new parents, it is almost always a temporary and harmless feature. However, understanding the role of lanugo also highlights its importance as a diagnostic marker for serious health conditions in adults [1].
Your next step: if you are concerned about your newborn's body hair or are noticing unusual hair growth as an adult, schedule a consultation with a pediatrician or primary care physician to discuss these symptoms.
Frequently Asked Questions
When does lanugo first appear?
Lanugo typically develops between the 16th and 20th weeks of pregnancy.
Why do premature babies have more lanugo?
Lanugo usually sheds in the last eight weeks of pregnancy, so babies born early have not yet completed the shedding process.
Is it safe to shave a baby's lanugo?
No. You should never wax, shave, or remove a baby's lanugo, as it will irritate their sensitive skin. It falls off on its own.
Where is lanugo most visible?
Lanugo is easiest to see on a baby's back, shoulders, tailbone, and neck.
Does lanugo grow on the palms?
No. Lanugo does not grow on the palms, soles of the feet, lips, or nails.
What happens to the lanugo after it sheds in the uterus?
The fetus swallows the shed hair along with amniotic fluid, and it becomes part of their first bowel movement (meconium).
Can adults grow lanugo?
Yes. In children, teens, and adults, severe eating disorders or malnutrition can cause lanugo, and in rare cases it has been linked to tumors or cancer.
What color is lanugo?
Lanugo can range from very light to dark, and it is often more visible on babies with darker skin.
How long does it take for lanugo to disappear after birth?
Lanugo usually falls off within the first two months of life.
What replaces lanugo?
After lanugo sheds, it is replaced by vellus hair, the fine "peach fuzz" hair that continues to help regulate temperature until adult (terminal) hair grows in.
Related Reading
Understanding Vellus Hair (Peach Fuzz) explains the fine vellus hair that replaces lanugo after birth.
Anorexia Nervosa: Symptoms, Causes, Treatment & Complete Guide covers the eating disorder that can cause lanugo to return in adults.
Premature Birth: Complete Guide to Signs, Causes, and Care explains why babies born early often still have lanugo and other needs.
Hypertrichosis: A Comprehensive Guide to Causes, Symptoms, and Management describes conditions that cause unusually heavy hair growth on the body.
References
Cleveland Clinic. Lanugo. Cleveland Clinic. November 14, 2025. https://my.clevelandclinic.org/health/body/22487-lanugo
Strumìa R, Varotti E, Manzato E, et al. Skin signs in anorexia nervosa. Dermatology. 2001;203(4):314-317. PMID 11752819. https://doi.org/10.1159/000051779
Slee PHTJ, van der Waal RIF, Schagen van Leeuwen JH, et al. Paraneoplastic hypertrichosis lanuginosa acquisita: uncommon or overlooked? Br J Dermatol. 2007;157(6):1087-1092. PMID 17941940. https://doi.org/10.1111/j.1365-2133.2007.08253.x
Medical disclaimer
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. The clinical information in this guide reflects source material last reviewed in November 2025.
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