Hypertrichosis is a rare and curious condition that causes excessive hair growth anywhere on a person’s body. Hypertrichosis is sometimes known as werewolf syndrome.

Hypertrichosis may be confused with hirsutism. Hirsutism is a more common condition that causes women to grow coarse hair in areas that men typically do, such as on their chin.

An image of Barbara Vanbeck, a lady with Hypertrichosis, by R. Gaywood, 1656.Share on Pinterest
An image of Barbara Vanbeck, a lady with Hypertrichosis, by R. Gaywood, 1656.
Image credit: Wellcome Images, 2014

There are many theories about the cause of hypertrichosis.

Congenital hypertrichosis may run in the family. It seems to be caused by genes that stimulate hair growth becoming abnormally active. In most people, the genes that caused extensive hair growth in humankind’s very early ancestors are now inactive because people do not need to be covered in hair to stay warm.

In people with congenital hypertrichosis, these genes get reactivated in the womb. There is still no known cause for this.

However, acquired hypertrichosis, which develops later in a person’s life, has a range of possible causes. Causes include:

  • malnutrition
  • poor diet or certain eating disorders, such as anorexia nervosa
  • certain drugs and medications, such as hair growth drugs, certain immunosuppressants, and androgenic steroids
  • cancer and cell mutation
  • autoimmune and infectious diseases affecting the skin

Sometimes, having a condition called porphyria cutanea tarda, which causes the skin to be extremely sensitive to UV light, may trigger hypertrichosis.

If hypertrichosis occurs only on specific places of the body, it may be due to chronic skin conditions, such as lichen simplex, which is associated with repeated rashes, itching, and scratching on a particular patch of skin. Increased blood supply (vascularity) in one specific area of the body can also cause the condition. Sometimes, symptoms of hypertrichosis appear in the area where someone wore a plaster cast.

The primary symptom of hypertrichosis is the presence of hair in greater amounts than is usual for a person’s age, race, and sex. Hair may also appear in unusual areas.

Not all hair produced by hypertrichosis is the same. Hypertrichosis can create three different types of hair:


Lanugo hair is long, thin, and very soft. It is similar to the hair on the body of a newborn baby. Lanugo hair will typically have no pigment and usually falls out a few weeks after birth. In people with hypertrichosis, this lanugo hair will remain until it is treated.


Vellus hair is usually short, soft, and faintly pigmented. These hairs may appear all over the body except in areas where there are no hair follicles, such as the mucous membranes, the soles of the feet, and the palms of the hands.


Terminal hairs are the darkest of the three types of hair. Terminal hair is usually thick, coarse, and long. It is often associated with hormones and is typically found on the face, armpits, and groin.

Women with hirsutism will often develop terminal hair on the face, back, arms, and chest.

The severity of hypertrichosis symptoms may increase or decrease with age.

There are many types of hypertrichosis, which are categorized according to how and when a person develops the condition.

Congenital hypertrichosis lanuginosa

The fine lanugo hairs appear in a fetus as usual but do not fade away after birth. Instead, the hairs continue to grow excessively in different areas of the body during the person’s life.

Congenital hypertrichosis terminalis

Instead of being born with lanugo or vellus hair, the baby may have terminal hair at birth that grows throughout their life. Affected individuals often have thick, fully pigmented hair that covers their body, including the face.

Acquired hypertrichosis

Acquired hypertrichosis develops later in life. It follows many of the same patterns of congenital hypertrichosis. Hair may be lanugo, vellus, or terminal hair, and it can appear in small patches or over the entire body.

Naevoid hypertrichosis

Excessive hair growth found on one or more patches of skin. A typical example is a very solid and bushy monobrow, also known as a unibrow.


Commonly mistaken for hypertrichosis, hirsutism affects up to 10 percent of women. Hirsutism is a term that relates to women who develop coarse terminal hairs in a typical male hair-growth distribution pattern, such as on the chin and chest. Women often develop hirsutism due to a hormone imbalance.

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Electrolysis or laser treatment may be recommended for long-term treatment.

Some people might be able to reduce their risk of developing certain types of acquired hypertrichosis by avoiding:

  • certain immunosuppressants
  • androgenic steroids
  • hair-growth drugs

There is no known cure for congenital hypertrichosis. Treatment involves managing the symptoms by removing the hair from the affected area.

Short-term methods of hair removal include:

  • shaving
  • plucking
  • waxing
  • bleaching
  • chemical epilation

Temporary solutions such as these can minimize the appearance of hair in the area, but the condition will cause the hair to grow back. Using these methods can also irritate the skin and cause rashes or ingrown hairs. It is also difficult to use some of these techniques in some regions of the body.

Electrolysis or laser treatment

Some people may opt for long-term treatments, such as laser epilation or electrolysis.

Electrolysis destroys the individual hair follicles using electrical charges.

Laser epilation does the same using laser light and is typically less painful than electrolysis. For some people, the treatment will result in permanent hair loss, though it may take multiple sessions to achieve the desired result.

Depending on the type, hypertrichosis is often accompanied by other symptoms and may be linked to an underlying condition.

There may be a genetic component to some forms of hypertrichosis, so anyone with a family history of the condition may wish to speak to a doctor.

Managing the symptoms or treating the underlying cause is the only necessary and readily available treatment for hypertrichosis.