Lanugo hair is extremely fine, soft, and downy, almost like peach fuzz but even thinner and lighter. It has no pigment or very little pigment, making it nearly colorless or very pale. Unlike the hair you’re used to seeing on your head or body, lanugo has no central core (called a medulla), which is why it feels silky and almost weightless to the touch. It’s the first type of hair the human body ever produces.
How Lanugo Differs From Other Body Hair
Your body produces three types of hair across your lifetime, and they look distinctly different from one another. Lanugo is the finest of the three. It’s soft, unpigmented, and so thin it can be hard to see unless light catches it at the right angle. Each strand is short, typically no more than a couple of centimeters, and lies flat against the skin.
Vellus hair, sometimes called “peach fuzz,” replaces lanugo after birth. Vellus hair is also thin and short, but it’s slightly more visible than lanugo and covers most of your body throughout life. Terminal hair is the third type: thicker, longer, coarser, and usually pigmented. This is the hair on your scalp, eyebrows, and (after puberty) your underarms, legs, and face. If you’ve ever seen the barely-there fuzz on a newborn’s shoulders or back, that’s lanugo, and it looks nothing like the dark, coarse hair you’d find on an adult’s arm.
Where It Appears on the Body
On a fetus or newborn, lanugo covers much of the body, including the back, shoulders, forehead, cheeks, and arms. It tends to be most noticeable on the shoulders and upper back, where it sometimes appears as a soft, downy coating. Palms, soles of the feet, and lips are typically bare. In premature babies, lanugo is often more visible because they were born before the hair had a chance to shed in the womb.
When lanugo appears in adults (more on that below), it tends to show up on the sides of the face, the back, and along the arms and legs. The pattern is similar to fetal lanugo but stands out more against adult skin, especially in people with darker complexions.
When Lanugo Normally Grows and Sheds
Lanugo first develops between 16 and 20 weeks of pregnancy. It serves as an anchor for the vernix caseosa, the waxy, protective coating that shields a baby’s skin from the amniotic fluid. Without lanugo holding it in place, the vernix would slide off.
The hair typically falls off during the last eight weeks of pregnancy. The fetus actually swallows the shed lanugo along with amniotic fluid, and it becomes part of the baby’s first stool. Babies born at full term may have little or no visible lanugo left. When traces remain, they disappear within the first two months of life as vellus hair gradually takes over.
Why Lanugo Sometimes Appears in Adults
Lanugo in adults is not normal and usually signals that the body is under serious nutritional stress. It’s one of the more recognizable physical signs of anorexia nervosa and severe malnutrition. The soft, downy hair growth typically shows up on the sides of the face, the back, and the arms and legs. The exact reason the body produces it again isn’t fully understood, but the leading theory is that it’s the body’s attempt to insulate itself when it no longer has enough fat to maintain core temperature.
This regrown lanugo looks the same as it does on a newborn: fine, pale, and soft. It’s not a sign of hormonal changes or masculinization. It’s purely a response to starvation. As nutritional status improves and body weight is restored, the lanugo gradually falls out on its own.
A Rarer Cause: Acquired Hypertrichosis Lanuginosa
In rare cases, excessive lanugo-type hair can appear across the face, neck, trunk, and limbs in a condition called acquired hypertrichosis lanuginosa. This is a different situation from malnutrition. It’s considered a paraneoplastic condition, meaning it can be associated with an underlying cancer. The hair looks the same as other lanugo (fine, soft, unpigmented), but it grows in areas that are normally hairless, like the forehead or nose, and it appears rapidly. People with this condition may also experience changes in taste, tongue inflammation, diarrhea, or unexplained weight loss. It’s extremely rare, but sudden widespread growth of fine, downy hair in an adult warrants medical evaluation.
How to Tell if Hair Is Lanugo
If you’re trying to identify whether hair on a newborn or on yourself is lanugo, look for these characteristics:
- Texture: Exceptionally soft and silky, finer than any other body hair you’ve felt.
- Color: Very pale, often nearly colorless. It won’t match scalp hair color.
- Thickness: So thin that individual strands are hard to see unless grouped together.
- Length: Short, lying flat against the skin rather than standing up or curling.
- Location: Shoulders, upper back, cheeks, forehead, and arms are the most common areas.
On a newborn, lanugo is completely harmless and temporary. On an adult, its presence is worth paying attention to because it typically reflects a body that isn’t getting enough nutrition to function normally.