Head lice: boring for doctors, important to patients

Editor, recent lice articles, including ‘BestTreatments’
(1), need updating. Without serious medical
investigation, head lice advice has sometimes relied
on speculation from a few entomologists. For eg,
advice to avoid hair-cutting originated from a
well-meaning but baseless suggestion in the 1970’s.

Resistance to pediculicides is well-documented.
Over-reliance on insecticidal treatment is putting
children’s health at risk. Non-drug measures should be
recommended. Unchecked transmission in schools is
causing higher prevalence. Routine screening is
advised. Without it, treatment decisions should take
into account repeated exposure. (2, 3).

Head lice are not harmless. They can cause dermal
injury and sensitization. Some people resort to
household poisons to relieve persistent cases. A
disproportionate amount of family time and money is
wasted. Millions (pounds) are spent in each of the UK,
USA and Australia on louse treatment annually (3).

Detection and removal of lice in some hairstyles is
more difficult than previously thought. Our group has
confirmed life-stage sizes as small as 0.6mm. Louse
camouflage and various hair factors can cause false
negatives and under-estimations. Without such
knowledge, clinical product assessments are
questionable (4).

Those who use a tiered diagnostic approach to
screening have found that manual treatment is more
successful than chemical. Fine-toothed combing is so
helpful that it is one of the tools by which therapies are
better assessed. Perhaps only head-shaving and
microscopic examination are the gold standard (2, 3,
4).

Dry-hair parting with a lamp-magnifier can help
practitioners to identify continuous egg deposition at
the scalp-hair margin outwards of chronic cases. Old
‘nit’ removal facilitates examination. Patients who
remove eggs may also find hidden lice. Further
fine-combing may helpfully confirm the live lice (2, 3, 4).

Removed head lice are alive but probably less of a
concern than direct transmission or unrecognised
relapses. Longer or thicker hair impedes detection and
removal of resistant infestations. Hair-shortening
improves comfort and access to residual lice.
Pediculosis is not self-limiting and undetected failures
(some relapsing monthly for years) are common in
longer hair of girls (3).

Lice can transfer instantly across hair tresses with a
vigorous rub. Severely neglected head lice may also
bite further down the body. New biological findings
place head and body lice in the same species. Body
lice carry typhus, relapsing fever and trench fever, which
are reemerging overseas. We suggest that
pediculicides should be reserved to assist with control
of such outbreaks. Lack of thorough screening and
treatment will allow more resistant lice to proliferate (5).

(1) 1. Nash B. Treating head lice BMJ 2003; 326:
1256-8.

(2) Bailey AM, Prociv P. Persistent head lice following
multiple treatments: Evidence for insecticide resistance
in Pediculus humanus capitis. Australas J Dermatol
2000; 41: 250-54.

(3) Bailey AM, Prociv P. Pediculus humanus capitis
infestations in the community: A pilot study into
transmission, treatment and factors affecting control.
Australian Infection Control 2001; 6: 95-101.

(4) Bailey AM, Prociv P. Head lice appearance and
behaviour: implications for epidemiology and control.
Australian Infection Control 2002; 7: 62-71.

(5) Bailey AM, Prociv P, Petersen HP. 2003. Head lice
and body lice: shared traits invalidate assumptions
about evolutionary and medical distinctions. Australian
Journal of Medical Science 2003; 24: 48-62.

Competing interests:  
None declared