Lucky you.
I've come back from holidays with two week old bites that have persisted for months afterwards.
( Davros' Granddad a voice of calm reason in a world of spastics., Wed 14 Sep 2011, 16:00, 1 reply, 15 years ago)

My immunity was hard won.
I spent the first eighteen years of my life being chewed every summer by Adirondack black flies and deer flies. (Google for them to read the tales of woe from others. They have been known to drive strong men mad.) After a period of years you develop a resistance to the bites, so your body can throw off the effect more quickly than most.

I don't recommend the experience.

I can, however, recommend Burt's Bees insect repellent. All herbal, inoffensive smelling, but very effective!
( The Resident Loon Not a demographic. Do not measure., Wed 14 Sep 2011, 16:06, Reply)