Lanugo

It's nice to come across a new word. Lanugo is the word for a type of body hair a foetus develops in the womb for protection and warmth. Babies typically shed lanugo before birth; however, some don’t shed it for several weeks after birth.

It is a soft, fine hair covering a foetus that usually falls off shortly after birth, but can develop in people with eating disorders or certain tumours.

Some newborns have lanugo covering their bodies at birth, especially if they’re born prematurely. 

Unborn babies develop lanugo between 16 to 20 weeks gestation. It covers their entire body except for places without hair follicles. Areas without hair follicles include their lips, palms, nails, genitals and soles of the feet. If a baby is born with lanugo, it should disappear on its own.

Children or adults with an eating disorder can develop lanugo hair. Experts believe this may happen because their body has difficulty keeping warm. It may be a sign that the person is extremely malnourished.

Some people with teratoma develop lanugo hair. Teratoma is a rare type of germ cell tumour. There have been a few cases of someone developing lanugo due to cancer.

What does lanugo do?

In the womb it plays a critical role in protecting the baby's skin and keeping them warm. Lanugo helps vernix (the waxy, cheese-like substance that covers the fpetus) stick to the skin. Vernix helps protect a fpetus’s body from amniotic fluid inside the womb. Amniotic fluid could damage their delicate skin without lanugo and vernix. When vernix is held in place by lanugo, it helps insulate the body and protect the skin. Lanugo also helps the baby stay warm and regulates their temperature until they develop enough body fat to serve this purpose.

It also helps the baby grow. This occurs because the lanugo hair sends vibrations to the baby’s sensory receptors when it moves. These receptors stimulate the baby’s growth. When lanugo falls off, the stimulation stops, and the baby’s growth slows down. Experts are not entirely sure how this happens, but continue to study this and other hormonal effects of lanugo.

When does lanugo fall off?

Most unborn babies shed lanugo shortly before birth. About 30% of all full-term babies are born with some lanugo. If your baby is born premature (before 37 weeks), they have a greater chance of having lanugo. It may take several weeks to go away, but lanugo will fall off on its own.

Lanugo typically falls off in the last eight weeks of pregnancy. Once it’s shed from the skin, it mixes in with amniotic fluid. Because your baby swallows amniotic fluid in the uterus, lanugo becomes part of the baby’s first food. They will pass the tiny hairs in their first poop at birth, called meconium.

After the baby sheds lanugo, it develops vellus hair, a fine, peach-fuzz-like hair. The vellus hair continues to help regulate temperature until adult hair (terminal hair) grows in.

Why do people with eating disorders get lanugo?

Lanugo is one of the side effects of anorexia nervosa, bulimia nervosa and other eating disorders in adults. It can indicate poor nutrition and malnourishment. Healthcare providers believe lanugo grows when a person doesn’t have enough body fat to keep them warm. In response, their body grows lanugo to help insulate the body.

What does lanugo look like?

Lanugo hair is soft, thin and feathery. If your baby is born with lanugo hair, they may look like they're coated in a layer of delicate fur. Lanugo can grow everywhere except the palms, lips, genitals, nails and soles of the feet. It’s easiest to see lanugo on your baby’s back, shoulders or tailbone, but it can grow anywhere there is a hair follicle.

What colour is lanugo hair?

Lanugo hair can range in colour from very light to dark. Your baby’s genetics play a role in how light or dark the hair may be. For example, if your baby has darker skin, lanugo may be more visible than in a baby with fair skin.

How do you treat lanugo on an adult?

Treating lanugo in adults involves treating the underlying condition. If a tumour causes lanugo, your healthcare provider will typically remove the tumor.

Should you remove lanugo hair?

No, you shouldn’t wax, shave or remove lanugo hair from your baby. This will irritate your baby’s highly sensitive skin. If you're an adult with lanugo, shaving or waxing may be an option. However, it will continue to grow back until the underlying condition is treated.