The best way I've found is to treat your clothes with permethrin spray . Here is the expensive way (diluted) to buy it:
Sawyer Permethrin Pump Spray - 24 oz. at REI.com
Here is the cheap way (concentrate):
Permethrin-10 Livestock & Premise Spray, 32 oz. - Tractor Supply Co.
I use DEET or Permethrin that I have bought at REI. I have seen Permethrin cheaper at the farm store but I have not bought it yet. The nice thing about Permethrin is that it will stay on your clothes through repeated washings.
You CAN see Chiggers, they look like little flakes of pepper. HARD to see but they can be seen if you have light colored clothes or skin. My work pants for non winter seasons are cheap, light colored fabric so I can see the spawn of the devil. If you have on clothes that are dark, like jean fabric, you will not see the Chiggers.
The WORST chigger infestation I have had was from looking at land to buy. I was at one place after work and I was wearing shorts and shoes with no socks. The driveway into the property was covered in Vetch which I call Tick/Chigger Weed. If you see Vetch around here it WILL be full of ticks and chiggers. I did not walk into the property because of the Vetch but I did walk on a neighboring parcel that had been clear cut which allowed me to see into the for sale lot. Then I talked with three neighbors and what they told me made me walk into the Vetch. I had planned to return later wearing proper clothing and chemicals but what the neighbors told me forced me into the Vetch....
Now, I am glad I ventured into and past the Vetch because I found out the seller was living in an shack made out of a bus. There were old cars, boats, 55 gallon drums, batteries, etc., along with the bus, on the property. What a mess. I also met another neighbor who had interesting things to say.
Then I drove home. About 10 minutes from the land, I started itching and looked down to see my legs covered in Chiggers. Surprise Surprise. I stopped at a gas station and bought the LAST can of OFF and sprayed the whole can on my legs! :shocked:

The DEET killed the chiggers but alas it was too late. I spent a good week doped up on Benydryl pills and cream.
I have tried every remedy I have heard and the only thing that works to stop the itch is an antihistimean pill and gel. Helps but does not cure. The best cure is scratching the heck out of the bite until they bleed white goo that seems to release the itching.

Not a real good solution to say the least.
The good news is that we have built up some "immunity" to the bites. We get bitten now and we get the red bites but the itching is not so bad and does not last long. We hired a guy with a bull dozer to push down some trees for us two summers back. He was wearing shorts and sandals. :shocked: I mentioned the ticks and chiggers but he was unconcerned. He said they chiggers did not bother him any more. Flip side is that I have been bitten quite a few times now, each time with dozens or hundreds of bites so the "cure" is not cheap. :laughing::laughing::laughing:
The cure is not total, we still will itch just not as bad, so we still use chemicals to fend these fiends from us.
Good Luck,
Dan