This may be a superficial skin irritation secondary to friction. Considering the location of the rash, have you been wearing tight shoes lately? Also, the rash between the thighs may be due to the friction caused by the thighs when they rub together. Is this applicable in your case?
The rash is non itchy, so it may not be a case of dermatitis or eczema. You may apply a mild Vitamin E cream over the area to reduce friction and dryness. Dry skin may easily break and readily irritates.
If the rash appears to change in character and if the rash appears in other parts of the body, then a prompt consult is necessary.
hi! i posted a question similar to yours and i didnt get any responses. i have had a non-itchy rash for about a month, and i have no clue where it started, but it is all over my body, mostly concentrated on the soft parts of my skin, eg., inner thighs, inner arms, lower back and trunk, and backs of legs. I went to the doctor today to get a referral to dermatology, but in the mean time, she thinks i may have pityriasis rosea. Google it and compare yours to the pics. mine are similar, but i dont remember a "herald patch." i hope this helps.