Pubic Pediculosis - Symptoms, Causes and Treatment

What is pubic pediculosis? The name pubic lice did not appear randomly, as Phthirus pubis is a parasitic insect of the same family as Pediculus humanus capitis, the famous lice that infests the scalp.

Pubic lice
Pubic lice

There are three types of lice:
  • Pediculus humanus capitis: the lice that infects the scalp.
  • Pediculus humanus humanus: a type of lice that infects the body's hairs.
  • Pthirus pubis: the pest that infects the pubic hair (boring).

The Phthirus pubis is an ectoparasite, or a parasite living outside of our body, unlike, for example, intestinal worms, which are endoparasites which live inside the body.

The Phthirus pubis is a lice about 1 mm in diameter, shaped like a crab, hence its other nickname: lice-crab. It is translucent, being very difficult to be identified with the naked eye, unless it has been fed recently, being full of blood, as in the image below.

Although it primarily affects the pubic region, pubic lice may be present in other areas with hairs on the body, such as underarms, beards, eyelashes, and eyebrows.

The Pthirus pubis does not usually affect areas that are not covered with hair.

The life time of the female of this lice is 4 weeks, when it reaches about 30 eggs (nits). Each egg takes about 1 week to hatch and bring new lice to life.


Pubic pediculosis is considered a sexually transmitted disease (STD). As the transmission is made through direct contact between the pubic hair during the sexual act, the use of a condom does not prevent the transmission, since it only covers the penis, leaving the entire pubic region exposed.

The annoying can be transmitted in ways other than the sexual way, but it is much less common. Non-sexual transmission cases may occur among people who share contaminated objects such as towels, personal clothing, and bedding.

The Pthirus pubis does not jump and does not fly. For transmission, intimate contact between the pubic regions is necessary for the lice to pass from one to the other. Pubic lice do not infest dogs, cats or other furry animals, and are therefore not sources of transmission of the disease.


The signs and symptoms of boring usually appear one week after the infection. The main one is intense itching in the pubic region. Burning sensation in this region is also common. If the lice are present in other areas of the body that have hairs, such as the beard, legs, armpits and chest, they may also be itchy.

The itching of the pubic pediculosis is more intense at night and the act of frantically scratching can cause skin sores. Some patients may also have enlarged lymph nodes in the groin area.

Small purplish spots or dark spots of 0.5 to 1.0 cm may appear in people with intense and prolonged infestation. They occur by reaction of the skin to the saliva of the pest, which contains substances anticoagulants. Some patients may also have enlarged lymph nodes in the groin area.

Parents of infants infected with Pthirus pubis on eyelashes or eyebrows should be investigated as they are often the source of infestation of the offspring. Towels and bed linen are often the source of the transmission in these cases.

Eyelash infestations usually have conjunctivitis and crusting on the ends of these hairs. In some cases it is also possible to see parasitic eggs glued to the eyelashes.


The pubic pediculosis can be treated with medicines similar to those used to treat head lice. As Pthirus pubis is an insect, its treatment is made with lotions containing insecticides suitable for use on human skin, such as Permethrin or Pyrethrin.

Usually, the cream or lotion is applied to areas of hair and rinsed after 10 minutes. Contact insecticides with mucous membranes, such as the glans or vagina, should be avoided. As with head lice, pubic lice and their nits can be removed manually with a fine comb.

Oral Ivermectin may be an alternative treatment if lotions do not achieve the desired effect.

Clothes and towels should be washed with hot water to avoid transmission to other people or recontamination of the patient. Also, in order to avoid recontamination, sexual partners should be treated, even if they are asymptomatic.

It is important to alert the patient that after the treatment and elimination of the pubic lice, the itching can still persist for up to 1 week.

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