My 6 years old has symmetrical rash on his low part of chest /abdomen it is small sized red rash that not itches or doesn't induce pain what can it be?

Call pediatrician: This could be lots of things including viral, bacterial, allergic, immune related, contact rash, other. Call doc, needs to be seen to be diagnosed.

Many possibilities: Many possibilities include reaction to virus (ie: viral exanthem), medication induced reaction, bite reaction, other rashes of childhood. Best to see dermatologist for diagnosis and treatment.