[My wife can walk through mid height grass in shirts and sandals and they don’t touch her. I walk through wearing boots and jeans and long sleeve shirt and they leave welts on my waist line and under arms.
Thing is with chiggers, they are too small to see, but leave red painful bite marks where they have injected you. And it itches, very painful itches.]
I press hard with a fingertip for several seconds. Helps with chigger bites, mosquito bites, and bee stings, probably by dissipating the saliva or venom into surrounding tissue.