I take anti histamines before I get bitten, and if I do, I take anti histamine and anti-inflammatories.
I carry an epi pen these days because of those bites, so I'm kind of wary.
I have found nothing that actively stops them biting. They'll eat their way through clothes to get to your flesh.
Deet, if you can find it in a decent strength, does kill them.....but so does a well aimed swipe, but you have to be aware of them to do that. They are sleekit little blighters and silent in flight.
Eurax cream really does help stop the itch. So does Antisan.
Sorry you're being afflicted with them just now. They say that every creature fills a necessary role in the scheme of things.....I cannot think of anything that these things bring to the table but their appetite, and honestly have a kill on sight policy for them.