6 to 12 million: Number of households affected by head lice each year, according to the CDC

$95: Approximate hourly cost to have a haredi woman from Brooklyn come to your house to pick lice out of your children’s heads

100: Species of insects the plague of lice in Exodus could have been referring to, since a taxonomy of insects was not actually invented until Aristotle’s time

9,000: Age of head-lice-infested mummy found in cave in Israel’s northern Negev. The mummy’s hair had been glued onto its skull with asphalt as an adhesive; the hair contained lice eggs identical to the kind found in Israel today.

lice comb 77 CE: Pliny the Elder writes: “Nits are destroyed by using dogs’ fat, eating serpents cooked like eels, or else taking their sloughs [shedded skin] in drink.” Yum.

Circa 1185 CE: Maimonides writes: “It is permitted to kill lice on Shabbat because they are [spontaneously generated] from sweat.”

2004 CE: Menlo Park, California, pediatrician Dale Pearlman develops protocol for treating today’s often-pesticide-resistant lice by smothering them with Cetaphil Gentle Cleanser.

7: Number of Germans infested with head lice invited to live for three weeks at Israel’s Museum of Bat Yam in 2008 in a performance-art meditation on German-ness, Jewishness, and the meaning of parasitism