Ear infection: If treated with antibiotics an ear infection can clear up in 36-48 hours.Untreated an ear infection may clear up in 5-7 days.However fluid fluid in the middle ear may take several weeks to clear up....Read more. Dr. Beth Summers Board Certified, Pediatrics 14 years in practice 122K people helped.ar infection: If treated with antibiotics an ear infection can clear up in 36-48 hours.Untreated an ear infection may clear up in 5-7 days.