Hypertrichosis: what it is, causes and hair removal options

Everybody has hair follicles over most of the body. In some, the hair is fine and almost invisible (vellus hair); in others it is thicker, darker and longer (terminal hair). DermNet defines hypertrichosis as hair growth that is excessive compared with what would be expected for a person's age, sex and ethnic background. It may develop all over the body or be isolated to small patches.

What counts as normal varies a great deal between families and populations, so the label is about a change from what is typical for that person or a pattern that is clearly out of proportion, not a single measurable threshold. DermNet gives a series of recognised patterns, which are summarised below.

• Congenital hypertrichosis lanuginosa: a very rare syndrome in which the fine, soft lanugo hair of the fetus keeps growing and persists through life. DermNet says only about 50 cases have been reported worldwide since the Middle Ages.

• Congenital hypertrichosis terminalis: all-over body hair, fully pigmented, which DermNet says is almost always associated with gum overgrowth (gingival hyperplasia).

• Naevoid hypertrichosis: a single, well-defined area of terminal hair, not usually linked to other disease. DermNet notes a "faun-tail" on the lower back may indicate underlying spina bifida.

• Hypertrichosis with birthmarks: seen with some congenital melanocytic naevi, vascular malformations and Becker naevi.

• Acquired hypertrichosis: hair growth that develops after birth, either localised or generalised, usually fine unpigmented vellus hair but sometimes pigmented terminal hair.

The two terms are often confused. The NHS describes hirsutism as women having thick, dark hair on the face, neck, chest, tummy, lower back, buttocks or thighs, and says it is usually linked to changes in androgen ("male" hormone) levels. The most common cause it gives is polyendocrine metabolic ovarian syndrome (the NHS's name for PCOS), with some medicines and other hormonal conditions as rarer causes.

The BAD leaflet on hirsutism explains the contrast: hirsutism is thick, coarse hair in women in sites such as the upper lip, chin, central chest, abdomen and lower back, whereas hypertrichosis is generalised excessive hair growth that is not in a gender-specific pattern. This matters because hirsutism often prompts a hormone check, whereas hypertrichosis prompts a search for other explanations such as medicines or general illness.

DermNet states that the cause of hypertrichosis is unknown in many cases. Congenital forms are believed to be genetic, either inherited or occurring through a spontaneous mutation. Acquired forms are linked with a range of triggers.

For generalised acquired hypertrichosis DermNet lists porphyria cutanea tarda, malnutrition such as anorexia nervosa, malignancy and drugs including ciclosporin, phenytoin, androgenic steroids and minoxidil. For localised acquired hypertrichosis it lists increased blood supply, repetitive rubbing or scratching (as in lichen simplex), temporary hair growth under a plaster cast, and repeated application of minoxidil, potent topical steroids, iodine or psoralens. Long eyelashes (trichomegaly) can arise from the eye-drop bimatoprost or from the cancer drug erlotinib.

A specific, uncommon form is acquired hypertrichosis lanuginosa. DermNet says it sometimes occurs in people who are later diagnosed with a cancer of some form, producing long fine silky hair confined to the face, particularly noticeable on the nose and eyelids, a pattern sometimes called malignant down. It adds that it is not known why a cancer causes this hair growth. Because it can be a sign of something else, new and unexplained hair growth of this type should be assessed.

Hair growth that is a lifelong family trait does not necessarily need investigation, but a change does. The NHS advice written for hirsutism is a sensible guide to timing: it says to see a GP if the hair growth is a problem for you, particularly with other symptoms such as irregular periods, and to ask for an urgent GP appointment if new thick, dark hair suddenly starts growing on the face and body, if the voice is getting lower or if muscles are getting bigger.

For hypertrichosis specifically, see a GP if the hair growth is new, spreading, started after beginning a medicine, or comes with weight loss, tiredness, poor appetite or other symptoms. A GP will usually review your medicines and may arrange blood tests. If a cause such as a skin condition or hormone problem is suspected, referral to a dermatologist or endocrinologist can follow.

The sources quoted here do not list emergency symptoms for hypertrichosis itself, because the condition is not an emergency. If hair growth appears together with severe illness, call NHS 111, or 999 if the problem is life-threatening.

Assessment is usually based on history and examination: when the hair growth started, which areas are involved, the type of hair, medicines taken (including creams, eye drops and supplements) and any other symptoms. Congenital forms are usually evident at or soon after birth. Because DermNet lists several drug and disease associations, a medicines review is an important early step.

Further tests depend on what the history suggests. They may include blood tests, and imaging if a malignancy or other internal cause is suspected. Most people with long-standing, stable hair growth will need no further investigation.

Where a cause is found, it is treated or removed, for example by changing a medicine that is responsible. Where a cause is not found or cannot be changed, DermNet says treatment is basically hair removal, with several methods available that need to be repeated regularly as hair continues to grow back, and that may cause scarring, dermatitis or hypersensitivity reactions.

The methods listed are repeated shaving, chemical epilation (depilatory creams), electrolysis and thermolysis, and waxing. DermNet says laser hair removal has more recently been proposed as a treatment option and appears to have fewer side effects and a longer-lasting result. The NHS, in its page on excessive hair in women, lists shaving, waxing, plucking, hair removal creams and bleaching as home methods, with electrolysis and laser hair removal as the two main longer-lasting treatments, and warns that they are not usually permanent, not usually available on the NHS and can be expensive, and that results are not the same for everyone.

Eflornithine cream, a prescription cream to slow hair growth on the face, is mentioned by the NHS as an option a GP may suggest for hirsutism; whether it is suitable for hypertrichosis is a question for the prescriber.

Visible hair growth can affect confidence and daily life, particularly when it is generalised or on the face. Talking to a GP about the emotional effect is reasonable; it is not just a cosmetic worry.

In general terms, the NHS investigates possible medical causes and reviews medicines, while hair removal for cosmetic purposes is usually self-funded. Laser and electrolysis are mostly provided privately, so it is sensible to research the practitioner's training and to ask about the risks, the number of sessions and whether treatment is suitable for your skin and hair colour, as the NHS cautions.