My mom had an allergic reaction to Zinc Oxide. What can I use now?

Agree, her wounds should be seen by a Nurse who does woundcare. Call her PCP and see if he can get "in home care" into the home and evaluate. That rash could be a baby rash type thing, and it maybe caused by yeast which is hard to get rid of. Easier to prevent. If yeast, may need a special cream.

The best way to keep rashes at bay is to make sure the area is kept dry. My Mom used to use cornstarch. Talc is not good for many reasons. It clumps as u said and it has fragrances. I never used it on my girls in certain areas. Never during a diaper change. A&D ointment is water soluable so disappears as soon as water touches it. Desitin stays on the skin longer but make sure the area is clean before using it. An aide I know recommends Almay stick deordorant in the fold areas. Takes away the redness and prevents it coming back. Me, I get red every so often and grab the Cortizone 10 cream. Clears it up for me.

A&D ointment. It is lanolin. Mild but very effective. But as always, ask a doctor first.

If you are simply looking for a soothing barrier cream then Wellskin Barriere Silicone Skin Cream is one that was recommended to us. Good old petroleum jelly works too. As for treating actual wounds - I agree with Fawnby, they are not a DIY project.

This is a question for a wound care expert. An untreated bed sore can take her out fast. Call the nurse at her doctor's office for starters. If she's on hospice, call them.