9 month old baby has been miserable the past couple of days. i thought she was teething but has now come up in a rash on body. no fever. ?

It happens: Many simple virus infections may generate little obvious symptoms until they end in a generalized rash. This would be the babies immune system depositing virus+antibody complexes near the skin surface where the temperature is cooler. If the kid gets back to her regular routine in a few days this was likely the cause. Food reactions might do something similar with raised hives.