Mods, can we get a better thread title? Something informative?
I can confirm the same thing on other folks. For me mosquito bites don’t really do much of anything, for a close friend they last for days as big red welts, even on her back where she can’t scratch. People seem to react differently.
Not scratching is trickier than it appears. I make an effort not to scratch, and during the day, I mostly succeed. I usually only get big welts when I get bit and night and wake up scratching or if I get bit somewhere that like my back that gets scratched by clothes or furniture.
To be clear, he doesn’t do it just by flexing his muscles-- I don’t know whether that’s possible or not. He reaches over and pinches the skin with his other hand.
I sometimes scratch the damn things.
Perhpas I’ll experiment when cooking outside tomorrow and make them bleed. See if they still go away.

You think I haven’t got days-long welts? Had plenty of em. And that’s how I learned the importance of not provoking those histamine reactions. Of course, tolerance matters a great deal too. And tolerance even has a feedback mechanism with scratching. The more tolerance you have, the less will be your urge to scratch, and the shorter the bites will last still. You say you have a high tolerance and shrug off mosquitoes? Try scratching. Do it. Enjoy it thoroughly, and enjoy it often. Then see what happens. It won’t be as bad for you as it is for your friend, but you can get your welts to stick around for days, no problem.
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For what it’s worth, my blood type is A+, and I’m not bothered by mosquitoes all that much here in the tropics. However, I was bitten enough to have contracted dengue fever one time.
As far as she says and I know she does not intentionally scratch them. And although they start off itchy, they turn to being just sore, non-itchy welts before too long.
We scratch chigger bites; that’s uncontrollable for both of us. It’s not like we have the ultimate in iron will.
I’m A+ and my father used to say he took me out fishing with him to act as a mosquito decoy. They just love me. I believe I could stand in the middle of a crowd of people and be the only one who gets bitten.
This is exactly my own experience. As a child, I used to get a dramatic allergic reaction to mosquito bites on my face or ankles.
Ah yes, but I think you can actually dig the annoying little creatures out with your fingernails.