RED BURNING RASH ,NO ITCH.

Probably some sort of contact dermatitis.   Try loose cotton based underwear, unscented baby powder.   What soap are you using.   If you're using the strong commercial soaps like Irish Spring, Lever 2000, Dial or other cheapies, toss them all out!

Use natual vegetable based soaps instead, they're about the same price and easy to find if you look for them.   There's a coconut based soap I see in grocery stores a lot that's $1.00 a bar.   Verbena Soapworks makes some very inexpensive natural american made soaps and the bars are absolutely huge and will last forever.

Also stay away from shampoos that have eucalyptus, or dandruff shampoos with zinc pyrithone or selenium sulfide (aka head & shoulders).

Finally toss your toothpaste if you're using Crest or Colgate or any other mass market brand.  Spend the $6.00 and get a natural toothpaste from the store, preferably without fluoride.