Untreated rhymes with:
maltreated, mistreated, accreted, maltreated, mistreated, accreted, competed, depleted, maltreated, meted, mistreated, repeated, superheated, uncompleted, undefeated, unseated
Untreated sounds like:
underrate, underrated, undertow, underwood, underwrite, underwrote, undeterred, unhindered, unitrode, untoward, untried, untruth