How Lice is Transmitted from One Person to Another
Lice are transmitted primarily through direct head-to-head contact, with indirect transmission through fomites (personal belongings) being much less common but possible. 1
Primary Transmission Route: Direct Contact
Head-to-head contact is the dominant mode of transmission for head lice (Pediculus humanus capitis), occurring when infested and non-infested individuals bring their heads close together during play, sports, or other activities. 1, 2
Lice cannot hop or fly—they only crawl, which is why direct contact is necessary for most transmissions. 1
Adult lice are the most mobile life stage and are most likely to initiate new infestations when they transfer between heads during direct contact. 3
Secondary Transmission Route: Fomites (Indirect Contact)
While the American Academy of Pediatrics emphasizes that indirect spread through personal belongings is much less likely and occurs rarely, it remains a potential route that should not be completely dismissed. 1
Evidence Supporting Limited Fomite Transmission:
Lice found on combs are likely to be injured or dead, and a healthy louse is unlikely to leave a healthy head unless there is heavy infestation. 1
Australian studies demonstrated the rarity of environmental transmission: examination of 118 classroom floors found no lice despite more than 14,000 live lice on the heads of 466 children using those classrooms. 1
Live lice were found on only 4% of pillowcases used by infested volunteers, further supporting that environmental transmission is uncommon. 1
Lice do not survive away from the scalp more than 1 to 2 days without a blood meal, limiting their ability to remain viable on fomites. 1
Evidence Supporting Some Fomite Transmission:
There is contradictory evidence suggesting fomites may play a more significant role than traditionally believed:
Laboratory studies have shown that lice can be readily dislodged by air movements such as blow-drying hair, combing, and toweling, with reports that static electricity from combing dry hair can physically eject an adult louse more than 1 meter. 1, 4
Passive transfer to adjoining fabric occurs frequently in laboratory settings, with lice transferring to fabric within 5 minutes. 4, 3
Lice can be transferred in the egg, instar, and adult stages through fomites. 4
Items That May Rarely Transmit Lice:
Important Clinical Caveats
What This Means for Prevention:
The major focus of control activities should be to reduce the number of lice on the head and to lessen the risks of head-to-head contact, rather than extensive environmental decontamination. 1
Children should be taught not to share personal items such as combs, brushes, and hats, though this is a secondary prevention measure. 1
Close proximity alone may suffice to increase the likelihood of new infestation, even without direct head-to-head contact. 4
Common Pitfall to Avoid:
Do not overemphasize environmental cleaning at the expense of treating the infested individual and their close contacts. The evidence clearly shows that lice on environmental surfaces are rare and usually non-viable, so excessive focus on cleaning carpets, furniture, and classrooms diverts attention from the primary transmission route. 1
Special Populations:
Preschool and elementary school-aged children are at highest risk due to frequent head-to-head contact during play. 1
Caregivers and household members of infested individuals are also at increased risk. 1
All socioeconomic groups are affected equally. 1
Key Distinction from Body and Pubic Lice
Head lice, unlike body lice, do not transmit any disease agents, making the infestation primarily a nuisance rather than a public health threat. 1, 6
Body lice can survive on clothing for up to 4 days without skin contact, making fomite transmission more relevant for body lice than head lice. 1, 7
Pubic lice are transmitted primarily through intimate/sexual contact. 8