What are body lice?
Body lice are small, parasitic insects found mainly on the clothing of infested people, and occasionally on their bodies or bedding. They spend most of their life on an infested person's clothing, crawling onto the skin to feed on the host's blood one or more times a day.
Female lice glue their eggs on the seams of clothing worn near the skin, where body heat allows them to hatch in about a week. Hatchlings develop to the adult stage in about nine days if they remain close to the host and have access to blood.
Most body lice are found on people who are living in conditions that are overcrowded without easy access to bathing and regular changes of clean clothes and bed linens.
In certain underdeveloped and war-torn parts of the world and places with poor sanitation and overcrowding, body lice have the potential to transmit the microbes that cause trench fever, louse-borne relapsing fever and louse-borne (epidemic) typhus.
Symptoms of body lice
A person affected by body lice often has itching, which is an allergic reaction to their saliva. The reaction to the bites may appear as small welt-like marks and, possibly, redness and swelling, particularly around the neck and on the torso. A heavy, long-lasting infestation may produce a darkening and thickening of the skin, fatigue and other symptoms. Scratching the bites can lead to infection.
Diagnosing body lice
Body lice are unable to burrow into the skin. Although a few body lice may be seen clinging to body hairs, most are on the clothing of an affected person. Body lice and their eggs are most abundant along the seams of clothes worn close to the body.
Someone with body lice typically will have 10 or fewer active lice on their skin at any one time. But the clothing may contain many dozens or hundreds.
Expected duration of body lice
The presence of body lice can continue indefinitely without treatment. Body lice can be eliminated immediately by bathing and changing into clean clothing. Occasionally, treatment of the affected person's skin with an insecticide is required.
Preventing body lice
Body lice are spread by direct contact with affected people and their bedding or clothing. To prevent infestation, avoid sharing clothes and bedding and close, prolonged contact with an affected person. Affected people do not need to be quarantined to avoid spreading body lice. Body lice can survive for several days on clothing removed from a person.
Treating body lice
The person needs to be washed from head to toe. The main way to eliminate body lice is by removing and washing or throwing away infested clothing and bedding.
Body lice and their eggs can be killed by washing clothing in very hot water, followed by drying these items in a clothes dryer set on high heat (more than 130 degrees Fahrenheit for at least 30 minutes). Dry cleaning or pressing the clothing with a hot iron will also kill the lice and eggs. Because body lice usually do not remain on the host, changing and/or washing clothes and bedding may be enough to eliminate these pests.
People with a lot of body hair may need to be treated with a pesticide (pediculicide) that can be applied to the body to make sure lice are eliminated completely. Over-the-counter pediculicides containing pyrethrum extracts or permethrin can be effective. Other pediculicides containing other classes of insecticides are available by prescription.
When to call a professional
If you suspect that you have body lice, consult with your doctor or public health officials to ensure proper diagnosis and to discuss treatment options.
Once body lice are eliminated, the skin irritation and other symptoms go away quickly.
Centers for Disease Control and Prevention (CDC)