May sound dumb, but my Mother used kerosene on us kids for chigger bites. She said if we got to scratching, would pull off their biting appendage, leave it under the skin and get infected, all I know is it worked.
The kerosene was to PREVENT bites (no self-respecting bug could stand it)! Mine used to paint our bare feet in the mornings before we went out to play in the yard to ward off hook worm and round worm larvae found in moist South Fla environs back in the day...
JC