Dear Straight Dope:
My dog blithely enjoys spending summer days outdoors, protected from fleas and ticks by a single monthly application of a small amount of liquid chemical to his skin. Meanwhile, I am feverishly scratching and slopping large quantities of rubbing alcohol and cortisone on the dozens of bites I have acquired from mosquitos and chiggers while walking across the lawn to turn on the sprinklers. The evil little critters that are chowing down on me don't bother the dog a whit: presumably they are also kept at bay by his monthly application of repellent (although it is possible that they are simply sated after feasting on me). Why isn't anyone marketing a once-a-month chigger/skeeter stop for humans?
SDStaff Doug replies:
The main problem with your idea is that fleas and ticks aren’t being repelled by the chemicals you squeeze onto your dog – the stuff kills the parasites or wreaks havoc with their life cycle, but it doesn’t repel them. Fleas and ticks live on their host animal 24/7, so the ointment works via sustained exposure; it’s typically designed to collect in your pet’s hair follicles and seep out gradually, creating an environment that’s ultimately lethal to the pests that try to dwell there.
By contrast, mosquitoes and chiggers don’t take up residence on humans but stay only briefly, so the same approach wouldn’t work. Even if there were some way of loading you up with enough supertoxic pesticide to kill mosquitos on contact for a month, it likely wouldn’t be too good for your health either. The anti-flea-and-tick stuff doesn’t in fact protect your dog from mosquitos – if he didn’t have fur, they’d be biting him, too – and for whatever reason, chiggers don’t seem to take much notice of dogs.
Incidentally, by the time you notice a chigger bite, the mite larva has generally already detached and dropped off – the itch is an aftereffect once they’ve stopped feeding.
SDStaff Doug, Straight Dope Science Advisory Board
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