My doctor said my corneal ulcer was healed & can go back wearing contacts but when i go back to wearing contacts, it get red again.what possible reason?

Recurrence?: You could have a recurrence of the ulcer or you may need to decrease your wear time. I would make a appointment asap with your eye doctor to rule out ulcer which is a serious condition.

Many: Your contacts may not be fitting correctly, you may have a problem with your contacts, you may be getting recurrent infections, you may have a defect from the past ulcer and the contact irritates it. You need to follow up with your contact specialist or and eye md.