Natural compounds have been suggested as alternative
sources for pediculosis capitis control. We aimed to
investigate the chemical composition and evaluate the
pediculicidal activity of spearmint, clove, cassia, thyme, eucalyptus,
and anise essential oils in addition to sesame oil against
human head lice in vitro. A filter paper contact bioassay method
was used by applying 0.25 and 0.5 mg/cm2 of each tested
oil to filter paper in Petri dishes with 15 females head lice and
another with ten nits. The lice mortalities were reported every
5 min for 180 min. The percentage of inhibition of hatch (PIH)
was used to calculate ovicidal activity by daily microscopic
inspections 5 days after the hatching of controls. Comparison
with the widely used pediculicide (malathion) was performed.
The most effective essential oil was spearmint followed by
cassia and clove with KT50 values of 4.06, 7.62, and 12.12
at 0.5 mg/cm2 and 8.84, 11.38, and 19.73 at 0.25 mg/cm2,
respectively. Thyme, eucalyptus, and anise were also effective
adulticides with KT50 values of 18.61, 32.65, and 37.34 at
0.5 mg/cm2 and 29.92, 43.16, and 45.37 at 0.25 mg/cm2,
respectively. Essential oils were also successful in inhibiting
nymph emergence. Spearmint oil was the most effective, with
a complete inhibition of emergence at 0.5 mg/cm2. Sesame
fixed oil did not show any adulticidal or ovicidal activity
against head lice in vitro. The observed insecticidal activity
was comparable tomalathion. The results herein described the
effectiveness of these essential oils as potential pediculicides
for head lice control. Incorporation of essential oils in
pediculicide formulations needs proper formulation and clinical
trials.