Pubic lice, commonly called crabs, look like tiny tan or grayish-white insects clinging to the base of pubic hair. Adult lice are only about 1.1 to 1.8 millimeters long, roughly the size of a pencil tip, so they can be difficult to spot without looking closely. On a woman’s body, the visible signs include the lice themselves, tiny oval eggs glued to hair shafts, intense itching, and sometimes small bluish spots on the surrounding skin.
What the Lice Look Like Up Close
Adult pubic lice have a distinctive shape that sets them apart from head lice or body lice. They are broader and flatter, with a round, wide body that genuinely resembles a miniature crab. A fully grown louse has six legs, and the front two are noticeably larger, shaped like a crab’s pincher claws. These oversized front legs are what the lice use to grip coarse body hair.
Their color ranges from tan to grayish-white when they haven’t fed recently. After feeding on blood, they can appear darker or reddish-brown. Because of their tiny size, you may need a magnifying glass or good lighting to see them clearly. They tend to stay very close to the skin surface, gripping the base of a hair shaft, and they move slowly compared to head lice.
Eggs and Nits on the Hair
Before you spot live lice, you’re more likely to notice nits, which are the eggs pubic lice lay. Nits are small gray-white ovals firmly cemented to individual hair shafts, usually within a few millimeters of the skin. They don’t brush off easily the way dandruff or skin flakes do. If you try to slide one along the hair, it resists because the female louse cements each egg in place with a glue-like substance.
A single female lays around 30 eggs over her 3 to 4 week lifespan. Eggs hatch after about a week, releasing nymphs that are even smaller than adults and nearly transparent. The nymphs go through three molts before reaching their full adult size. This means a new infestation can look like almost nothing at first, with only a few barely visible nits, then become more obvious over the following weeks as the population grows.
Skin Changes You Can See
The most common visible sign beyond the lice themselves is irritated, reddened skin from scratching. Pubic lice bites cause persistent itching, and the scratching that follows can leave small red marks, raised bumps, or broken skin across the pubic area, inner thighs, and lower abdomen.
A more distinctive sign is the appearance of small blue or slate-gray spots on the thighs or lower abdomen. These spots, sometimes called sky-blue spots, are caused by a substance in the louse’s saliva that interferes with normal blood clotting beneath the skin. They’re painless and flat, and they can linger even after the lice are treated. Not everyone develops them, but when present, they’re a strong visual indicator of a pubic lice infestation rather than another skin condition.
You may also notice tiny dark specks on your underwear. These are louse droppings, which are essentially digested blood. Small rust-colored spots from bite sites can appear on undergarments as well.
Where Crabs Appear on the Body
On women, pubic lice most commonly infest the coarse hair of the pubic region, including the mons pubis, labia, and the area around the anus. But they aren’t limited to that zone. They can spread to any area with coarse body hair: armpits, leg hair, the abdomen, and even the eyebrows or eyelashes. When lice reach the eyelashes, the nits are visible as tiny specks at the base of the lashes, and the surrounding skin often becomes red and crusty.
Pubic lice do not infest the scalp. The hair on your head is too fine and closely spaced for them to grip. They need the wider spacing of coarse body hair to survive.
How to Tell Crabs Apart From Other Conditions
Several common skin issues can mimic the itching and redness of pubic lice. Folliculitis, which is an infection of individual hair follicles, produces red bumps or small pus-filled spots that can look similar to bite marks. Contact dermatitis from soaps, detergents, or razors also causes redness and itching in the pubic area. Scabies, another parasitic infestation, causes intense itching that’s often worse at night and produces thin, irregular burrow lines in the skin rather than visible insects.
The key difference is that with crabs, you can find the lice or their nits on the hair itself. If you part the hair in a well-lit area and look closely at the base of the shafts, you’ll see either the tiny crab-shaped insects or their oval eggs. No other common skin condition leaves visible organisms attached to the hair. A healthcare provider can confirm the diagnosis quickly using a dermatoscope, which is a specialized magnifying tool that makes the lice and nits easy to identify.
What a Healthcare Exam Looks For
During a clinical exam, a provider looks for three things: live lice at the base of the hair, nits attached to hair shafts, and scratch marks or signs of secondary skin infection. Excessive scratching can break the skin and allow bacteria in, leading to crusted or oozing patches that look worse than the lice infestation itself. If the area around the bites looks increasingly red, swollen, or warm, that suggests a bacterial infection has developed on top of the original problem.
For young children who may have been exposed, providers also examine the eyelashes with a high-powered magnifying glass, since pubic lice in that area can cause eye irritation and swelling that looks like pink eye but doesn’t respond to typical treatments.