Definition, Description, And Etiology

This affection is due to the Phthirius or Pediculus pubis, the general form and appearance of which is shown in Fig. 26.

This insect exhibits a preference for the pubic region. It is not, however, confined to this locality, as we have found it in the eyebrows, beard, and axilla, as well as the hairy parts of the chest, thighs, and legs. It is, I believe, never met with on the scalp. The insect derives its nourishment from the skin, to which it is usually found strongly attached. It lays its eggs, however, among the hair, to which it firmly glues them.

The affection is most frequently contracted during sexual intercourse, but sometimes by wearing infected clothing, sleeping with an infected person, or in a bed where one has slept, and probably also at the water-closet.

The presence of the insect gives rise to more or less pruritus of the affected regions, and commonly leads to inspection of the parts and detection of the cause.


Pruritus of the hairy parts of the body, other than the scalp, should always raise suspicion as to the presence of the insect, and a careful examination will settle this question without difficulty.

Fig. 28.   Phthirius pubis, or crab louse.

Fig. 28. - Phthirius pubis, or crab-louse.


The patient may, if he chooses, be freed from his ailment in half an hour, or if he prefers less efficient treatment, may fuss with it for months.


If the eyebrows are involved, carefully pull out or snip off every hair to which the eggs of the insect are attached. Then thickly smear the part with mercurial ointment. The whiskers, beard, and moustache, if those parts are involved, may be treated in the same manner. The pubic region and other hairy parts should then be carefully examined, and the affected regions should be shaved with a razor. If a warm bath, with soap and a scrubbing-brush, be then employed, the probability is that no further treatment will be necessary. The less efficient means of cure are the employment of Ungt. Sulphuris, Ungt. Hydrargyri, etc., or lotions of bichloride, tincture of delphine, petroleum, kerosene, and the like.