If you have access to a WOC Nurse, I recommend having them examine your skin and make some suggestions. If it looks bad enough, they may recommend a dermatologist.

You may be having a temporary reaction to the adhesive on the bottom of the base plate, and it will eventually get used to it and stop being itchy/red and using allergy medication to help with itching may be good enough until it stops on its own.

If it is a persistent issue, you may need to try different brands for your ostomy base plate/bag system. You can get free samples from all the manufacturers (Hollister, Coloplast, ConvaTec, etc). You could call your current one to see if they have other systems for people who may need a different type of adhesive.

However best to start with a WOC Nurse and go from there