I had a csection and was giving morphine. my lip started itching and my cheek really bad and now i have what looks like feaver blisters ..whats wrong?

When?: Did the lip itch and cheek itch start right away? Did the blisters come quite soon after the morphine was delivered? Do you remember something else that was given to you? Some of those signs relate to an allergic reaction (mild) and it would not be a bad idea to consult with your delivering physician to find out. If all this started a couple days after that deliver...Then likely not related.

Canker Sores: are the most common oral lesions. Individual ulcers typically last 1-2 weeks. The condition is usually self-limiting. Try to keep adequate oral hygiene as possible. If concerned, see your dentist.

How long?: If it is herpes hsv1 then the antiviral pill can be effective if started on the first or second day. After that the benefit decays rapidly. A dermatologist can help you.