Lice Bites: Head Lice and Body Lice Identification

Itching is the main symptom, and it is a reaction rather than an injury. The CDC calls itching the most common symptom of head lice infestation, along with a crawling or tickling sensation in the hair, restlessness and disturbed sleep, and scalp sores from scratching that may become infected. For body lice, the CDC describes intense itching and a rash caused by an allergic reaction to the bites.

The delay is the part that surprises people: the CDC says it may take four to six weeks for itching to appear the first time a person has head lice. So by the time the itching starts, the infestation is well established — which is why school screenings look for the insects and the eggs rather than waiting for symptoms.

Prolonged body lice infestation can cause the skin to thicken and darken in heavily bitten areas, according to the CDC.

The CDC gives usable sizes. Adult head lice are roughly 2 to 3 mm long, about the size of a sesame seed. Nymphs, the young lice, resemble adults but are much smaller — pinhead-sized. Nits, the eggs, attach firmly to hair shafts within a quarter inch of the scalp, and are frequently found behind the ears and near the back of the neck.

That quarter-inch rule is the most practical part. Something stuck firmly to a hair shaft close to the scalp behaves like a nit; something that slides along the hair is more likely to be dandruff or hair product residue. Lice live mainly on the head but can also be found on eyebrows and eyelashes.

Penn State Extension notes that most biting pests can be seen without magnification. If you comb one out onto a pale surface, photograph it and the app identifies it.

The CDC describes adult body lice as 2.3 to 3.6 mm long, about the size of a sesame seed, with six legs, tan to greyish white. The key difference from head lice is where they live: body lice inhabit clothing and bedding, and an infestation is identified by finding eggs and crawling lice in the seams of clothing rather than on the body.

The CDC says body lice typically affect people who lack access to regular bathing and clean clothing, including people who are homeless, refugees and disaster survivors. They can transmit epidemic typhus, Bartonella quintana infection and epidemic relapsing fever, which head lice are not described as doing.

Treatment centres on hygiene: bathe and change into clean clothes at least once a week, machine wash infested items in hot water at a minimum of 130°F and dry on high heat. The CDC notes pediculicide medication may be prescribed in some cases but is not necessary with proper hygiene practices.

For head lice, the CDC names direct hair-to-hair contact as the primary transmission route, with spread also possible through shared clothing, combs, brushes or bedding. That ordering matters: the head-to-head route is the main one, so shared hats and hairbrushes are a smaller factor than the way children put their heads together.

For body lice, the route runs through clothing and bedding, which is why the CDC's control advice is about washing and changing rather than about treating skin.

University of Kentucky entomology lists lice among the causes of unexplained bites, alongside bed bugs, fleas and several mites, and its diagnostic approach applies here as much as anywhere: the deciding question is whether anyone has actually seen or captured the insect.

The CDC recommends consulting a healthcare provider if you are uncertain about the diagnosis before pursuing treatment. That is worth taking seriously, because treating for lice that are not there is common and unhelpful.

The NHS advice for bites and stings applies to the scratching damage: see a pharmacist if an area shows signs of infection such as heat, redness, pus, swelling and pain. The American Academy of Dermatology says to see a board-certified dermatologist right away for a rash, fever, headache or body aches after a bug bite, or for a bite that looks infected.

Body lice are also a marker of circumstances rather than hygiene failure alone — the CDC ties them to a lack of access to bathing and clean clothing. Addressing that is part of the treatment. Nothing on this page is a diagnosis.