Version May 2024
INTRODUCTION — Pediculosis corporis (body lice) is a parasitic infestation caused by Pediculus humanus humanus, a hematophagus (blood-feeding) insect. In contrast to the lice responsible for pediculosis capitis (head lice) and pediculosis pubis (pubic lice), pediculosis humanus humanus primarily resides in clothing rather than on the skin or hair (picture 1A-C). Affected patients present with widespread pruritus, frequently involving the truncal areas (picture 2A-B).
The clinical findings, diagnosis, and treatment of pediculosis corporis will be discussed here. Pediculosis capitis (head lice) and pediculosis pubis (pubic lice) are reviewed separately.
●(See "Pediculosis capitis".)
●(See "Pediculosis pubis and pediculosis ciliaris".)
PEDICULUS HUMANUS HUMANUS — Pediculus humanus humanus (the body louse) is the causative organism of pediculosis corporis. Pediculus humanus humanus is also known as Pediculosis humanus corporis.
Pediculus humanus humanus and Pediculus humanus capitis (the causative organism of pediculosis capitis) are closely related variants of the same species (figure 1). At 2 to 4 mm in length, Pediculus humanus humanus is slightly larger but similar in morphology (figure 1 and picture 3A-B).
Unlike Pediculus humanus capitis, Pediculus humanus humanus lives in clothing and lays eggs (commonly referred to as "nits") along clothing seams rather than residing on the human host. The louse visits the host's skin to feed and can survive for up to three days without a blood meal [1].
RISK FACTORS — Pediculosis corporis is most prevalent in locations where poverty, crowding, and limited access to personal hygiene necessities (eg, water, products or equipment for frequent clothes washing, bathing facilities) favor spread and multiplication of the parasite. Bed-sharing is one factor that may contribute to the spread of body lice among individuals.
In resource-rich regions, pediculosis corporis most often affects people who are experiencing homelessness (particularly individuals not residing in shelters and without access to bathing facilities) [2].
CLINICAL MANIFESTATIONS — Pruritus and visible skin changes are the primary clinical manifestations.
●Pruritus – Pruritus is the chief complaint, although some affected individuals may be asymptomatic. Pruritus is thought to result from an allergic or inflammatory reaction to louse saliva [3].
●Skin changes – Cutaneous findings often include linear excoriations on the trunk and neck. Areas of postinflammatory hyperpigmentation and/or skin lichenification (skin thickening) may also be present (picture 2A-B). Close inspection will sometimes reveal hemorrhagic puncta or wheals from fresh bites.
Skin changes tend to be concentrated around the waist and in the axillary folds, areas where clothing seams contact the integument.
●Associated physical findings – Signs of cutaneous secondary infection or concomitant infestations (eg, scabies, pediculosis capitis, pediculosis pubis, fleas) may be present [3]. (See 'Secondary skin infection' below.)
COMPLICATIONS — Potential complications of pediculosis corporis include cutaneous and systemic infections.
Secondary skin infection — Pruritus-related scratching and excoriations may contribute to secondary infection of the skin [3]. Honey-like crusting and erythema may be present in the setting of staphylococcal infection. (See "Impetigo".)
Disease transmission — Pediculus humanus humanus can serve as a vector for infectious diseases, such as [4-6]:
●Epidemic typhus – Related to transmission of Rickettsia prowazekii (see "Epidemic typhus")
●Febrile illness (eg, trench fever) or endocarditis – Related to transmission of Bartonella quintana (see "Bartonella quintana infections: Clinical features, diagnosis, and treatment" and "Endocarditis caused by Bartonella")
●Louse-borne relapsing fever – Related to transmission of Borrelia recurrentis (see "Clinical features, diagnosis, and management of relapsing fever")
DIAGNOSIS — The diagnosis of pediculosis corporis is made by visual identification of the louse or its eggs (nits) in the patient's clothing. Often, lice can be found in clothing seams. Less often, lice are seen crawling or feeding on skin (picture 1B-C).
Lice may be visible with the naked eye, but a magnifying lens is helpful for finding lice and eggs [6].
DIFFERENTIAL DIAGNOSIS — The differential diagnosis of pediculosis corporis includes scabies, dermatitis, and other causes of pruritus. The visual detection of lice distinguishes patients with pediculosis corporis. Pediculosis corporis may also coexist with common pruritic disorders.
●Scabies – Scabies can present with widespread pruritus and excoriations. The identification of scabietic burrows and erythematous papules in classic areas of involvement (eg, web spaces of the fingers, wrists, and male genitalia) suggest the possibility of scabies (picture 4A-B and figure 2). Scabies mites are much smaller than lice and are undetectable on examination with the naked eye. A skin scraping or dermoscopy may assist in the diagnosis. (See "Scabies: Epidemiology, clinical features, and diagnosis".)
●Other disorders – Examples of alternative causes of widespread pruritus include atopic dermatitis; contact dermatitis; and pruritus secondary to systemic disease, psychiatric disease, or neurologic disorders. (See "Overview of dermatitis (eczematous dermatoses)" and "Pruritus: Etiology and patient evaluation".)
MANAGEMENT — The eradication of lice through increased hygiene practices is the mainstay of therapy for pediculosis corporis [6]. However, efficacy data for interventions are limited and insufficient for definitive conclusions on the most effective approach to therapy.
General approach — Measures to improve clothing and skin hygiene and manage symptoms are considered sufficient for most patients. Use of pediculicides in addition to these measures is primarily reserved for the infrequent patients in whom lice or nits are found directly on the body. (See 'Patients with lice or nits detected on body hair' below.)
Eradication of lice
●Eradication of lice from clothing and linen – For the successful eradication of infestation, the patient's contact with lice-infested clothing or other linens should cease. Key measures include:
•Provision of a complete change of clean, noninfested clothing
•Laundering or discarding of infested clothing, bed linen, and towels – Items should be washed in hot water (temperature should reach at least 130°F [54.4°C]) and dried on a high heat dryer setting, dry cleaned, or discarded [6,7]. Ironing clothing with particular attention to the seams will also kill lice on fabrics.
Continued laundering and changing of clothing at least once weekly may support cessation of infestation [6].
●Skin cleansing – The patient should bathe thoroughly. This may aid with removing lice that are actively feeding on the skin and may prevent the transfer of these lice to clean, noninfested clothing.
Pruritus — Use of a low-potency or medium-potency topical corticosteroid after the implementation of measures to eradicate lice may be helpful for providing relief from pruritus (table 1). The topical corticosteroid can be applied to pruritic areas twice daily for a few days to provide symptomatic relief.
Secondary skin infection — Appropriate antibiotic therapy should be administered to patients with secondary skin infections. (See 'Secondary skin infection' above.)
Patients with lice or nits detected on body hair — Although Pediculus humanus humanus generally resides and lays eggs in clothing, occasionally lice or louse eggs (nits) are found on body hair. For these patients, some authors, including ourselves, advise treatment with a topical pediculicide in addition to hygiene measures [1,8]. However, superiority of this approach over hygiene measures alone has not been proven.
The same topical pediculicides that are effective for killing head lice are also considered to be effective for killing body lice [6,9]. However, for pediculosis corporis, the pediculicide is applied to the entire body (excluding the face) rather than only to scalp hair. (See "Pediculosis capitis", section on 'Topical pediculicides'.)
The best approach to pediculicide therapy is unclear. Our preferred pediculicide regimen is a single application of permethrin 1% lotion to the entire body (excluding the face). The lotion is rinsed off with water after 10 minutes. An approach similar to the permethrin regimen for scabies (an 8- to 10-hour application of permethrin 5% cream) has also been utilized in clinical practice. (See "Scabies: Management", section on 'Permethrin'.)
Topical permethrin has a favorable adverse effect profile and, in the United States, is relatively inexpensive compared with some other commercial topical pediculicides.
Examples of alternative pediculicides include topical malathion, topical spinosad, and topical ivermectin. (See "Scabies: Management", section on 'Permethrin' and "Pediculosis capitis", section on 'Topical pediculicides'.)
Due to risk for severe toxicity, topical lindane should not be used for treatment of lice infestation. (See "Pediculosis capitis", section on 'Lindane'.)
Other interventions — Although limited data suggest that oral ivermectin and permethrin-impregnated undergarments might reduce the prevalence of louse infestation in affected populations, additional study is necessary to clarify whether such interventions should play a role in the management of pediculosis corporis. Benefit of these interventions may be transient.
●Oral ivermectin – In an uncontrolled study, a three-dose regimen of oral ivermectin (at 12 mg per dose) was associated with a temporary reduction in the prevalence of body louse infestation in a cohort of patients experiencing homelessness (28 of 33 patients [85 percent] infested at day 0 versus 5 of 27 patients [19 percent] at day 14) [10]. However, this degree of benefit was transient. By day 45, infestation was present in 17 of 28 patients (61 percent).
●Permethrin-impregnated clothing – Permethrin-impregnated undergarments and socks were associated with a transient reduction in body louse infestations in one small randomized trial. In the trial, 73 individuals with pediculosis corporis who were also experiencing homelessness were randomly assigned to wear either permethrin-impregnated underwear (t-shirt, underpants, and socks) or identical untreated underwear for 45 days [11]. Although there was a greater likelihood of louse eradication at day 14 in the permethrin group (28 versus 9 percent), the difference between the two groups was no longer statistically significant at day 45 (28 versus 27 percent). In addition, an increase in permethrin-resistant body lice was detected in the permethrin group at the end of the study.
Close contacts and community — Individuals who reside with an individual with active infestation should avoid sharing clothing or bedding with that individual. Cohabitants and close contacts should be assessed for the possibility of infestation.
On a case-by-case basis, public health measures may be appropriate for attaining control in communities with a high prevalence of infestation and transmission, given the potential for the body louse to transmit disease [6]. Mass screening and interventions such as mass treatment of clothing via boiling, laundering, or pesticide application may be appropriate in some settings [12].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pediculosis".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Lice (The Basics)")
●Beyond the Basics topics (see "Patient education: Head lice (Beyond the Basics)" and "Patient education: Pubic lice (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Etiology – Pediculosis corporis (body lice) is a parasitic infestation caused by Pediculus humanus humanus (the body louse). Unlike lice associated with pediculosis capitis (head lice) and pediculosis pubis (pubic lice), Pediculus humanus humanus lives on the clothing, rather than on the skin, of infested individuals (picture 1A, 1C). (See 'Pediculus humanus humanus' above.)
●Risk factors – Pediculosis corporis is most prevalent in locations where there is poverty, crowding, and limited access to personal hygiene necessities. In resource-rich regions, pediculosis corporis most often affects people who are experiencing homelessness. (See 'Risk factors' above.)
●Clinical manifestations – Pruritus is the primary symptom of pediculosis corporis. Additional findings may include excoriations, postinflammatory hyperpigmentation, and skin lichenification (picture 2A-B). Patients may also have signs of secondary infection or concomitant infestation. (See 'Clinical manifestations' above.)
●Complications – Secondary skin infection is a potential complication. In addition, Pediculus humanus humanus can serve as a vector for infectious diseases, such as epidemic typhus, Bartonella quintana-related fever or endocarditis, and louse-borne relapsing fever. (See 'Complications' above.)
●Diagnosis – The diagnosis of pediculosis corporis is made through the visualization of lice or nits on clothing or skin. Although body lice are visible to the naked eye, a magnifying glass can be helpful for identifying lice and eggs (picture 1B-C). The differential diagnosis includes scabies, dermatitis, and other causes of pruritus. (See 'Diagnosis' above and 'Differential diagnosis' above.)
●Management – For most patients with pediculosis corporis, infestation can be eradicated through increased hygiene practices. Management involves discarding, laundering (in hot water), or ironing infested clothing and bedding. For patients with bothersome pruritus, we suggest a short course of treatment with a low-potency or medium-potency topical corticosteroid (table 1) (Grade 2C).
For the occasional patients who are found to have lice or nits on body hair, we suggest treatment with topical permethrin 1% lotion (Grade 2C), in addition to laundering or discarding clothing and bedding. However, superiority of combining hygiene measures with pediculicide therapy has not been proven, and treatment with hygiene measures alone is a reasonable alternative. (See 'Management' above.)
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