This is a disgusting & potentially embarrassing subject, but I've just gotta know: I've been reading about the killing of lice; prescription-strength pyrethrins are 5.0% in the top 3 non-lindane lice killers.

Yeah, I suspect an infestation; however, given the costs and uncertainties associated with testing (which seems designed to produce a relatively high percentage of false negatives), it seems more logical to perform a thorough initial treatment and then observe the results.

"Cheapo" OTC lice killers (about 0.33% pyrethrins) go for about $2.50 per ounce. OTOH, garden-duty 5.0% pyrethrins are less than $1.69 per ounce for quart-size containers.

Given the area one living in a carpeted house is likely to have to clean-up, doesn't it make sense to just get the garden stuff and use it for both treating the carpet and the infested humans?
Also, there are "6.0% pyrethrins" pesticides out there -- and I *really* want to kill *all* of whatever no-see-um that's bothering me -- and it's cost-competitive with the 5% stuff. Should I just "up the voltage" (line from "Real Genius"), stick with the 5% stuff?

My plan is to follow the guidelines for treating with 5%.
Oh, and how critical is the "exactly 10 minutes" the 5% solution is supposed to be left on the patient's body?

I can understand not wanting to leave it on less time (ineffectiveness), but given the slowness of pyrethrin absorption and the readiness of its excretion (blah blah blah), what could it hurt to leave it on 15-20 minutes, instead?

Oh, and I suppose it's worth mentioning: I am not at all concerned for the alleged potential carcinogenic effects of pyrethrins:

I'm not going to ingest 1000-or-more mg/kg daily for 2 years in order to see whether I develop a tumor. Mine is a "shock and awe" plan, with a definite timetable for withdrawal.
Please note the differences in concentrations for the priced solution alternatives: the OTC stuff is roughly 1/15 the concentration of the prescription stuff (0.33% vs 5.0%).

It's only somewhat fallacious to suggest I'd need 15x as much of the OTC stuff to do the same job -- which makes the contrast more than $37.87 per equivalent dose for the OTC stuff, versus less than $1.69 for the garden-strength stuff.

If I figure I need 10 ounces of the garden-strength stuff, my cost for materials is on the order of $17 for the garden-strength stuff -- or $379 for the OTC stuff.

I like my health, but I also like the idea of saving $362.

It's your health and it isn't worth the 81c difference.

if your willing to risk your health, then i say go for. what could it hurt?