What causes a rash, red, blotchy, then solid red, on trunk, chest. not itchy.hot. no new products on skin or injested.

See Dr.: Unfortunately, rashes are almost impossible to diagnose over the computer. There are multiple causes of rashes, ranging from various allergies to diseases such as lymes, etc. The rash could be somehting simple or something associated with an other underlying condition. See a dr. To get a clinical exam, as the majority of rashes are easy to treat once properly diagnosed. Goodluck.