Why do chiggers go away faster if you don’t scratch?

Dear Straight Dope: Over the years of wandering around in the woods I have had several encounters with “chiggers”, which some folks in the south refer to as “red bugs.” Once these little SOBs latch on to you they begin to itch like you can’t believe. I know from experience that if you scratch, they will stay with you for a long time, weeks or even months, but if you can refrain, no easy task, they can be gone within about a week. My question is, what are they, what causes the itch and is the itch part of a mechanism to prolong their stay? Ed

Doug replies:

SDSTAFF Karen interjects:

I always heard that you are supposed to scratch chiggers, because they lay their eggs in your skin, and you have to scratch them out. Otherwise you are a permanent home for chiggers.

I am not a bug expert. And I’ve never had chiggers.

SDSTAFF Doug replies:

Karen, unfortunately, has heard wrong about chiggers. Chiggers are mite nymphs, and since they are sexually immature, can’t lay eggs. What they do is burrow in and feed for a few days, then drop off to complete the life cycle. The histamine response (the itch) is to increase blood flow to where they’re feeding, same as with mosquitoes and other blood-feeding critters. The reason it takes longer for the itch to go away if you keep scratching is not because the chigger is still there (it’s gone after a few days), but because YOU KEEP SCRATCHING. Itches are self-perpetuating–the more you scratch them, the longer they persist, even after the original stimulus is long gone, as in the case of chiggers.

Doug

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Why do chiggers go away faster if you don’t scratch?

A STAFF REPORT FROM THE STRAIGHT DOPE SCIENCE ADVISORY BOARD