What shall I put on my Mom's redness areas left by a large band aid?

Perfect timing. Lately, the past few few weeks, Dad's been getting rashes where the paper tape is holding his catheter in place on his upper thigh. I've been moving that tape on a daily basis. Pretty soon, he won't have any smooth unaffected skin to tape it to. I will stop by the drugstore and see about the non adhesive wrap and the Nexcare gentle/delicate skin tape.

We use non-stick gauze pads on my grandpa, and then a gentle light-adhesive tape to adhere them, because his skin is too delicate for band-aids anymore. We usually buy Nexcare. The tape says something like "gentle" or "for delicate skin."

Cwillie that would be my guess, allergy to latex in bandages or the adhesive. Also good call on very tender skin. Try using a gauze type pad, no adhesive then the non adhesive wraps to attach it to the thigh.

Hydrocortisone, if an allergic reaction may help. There is no help for old thin skin. Thy the non adhesive wrap with a gauze bandage. The wrap is very cool sticks to itself not to the skin. And I don't think it contains latex.

I'm wondering if she might be having an allergic reaction to the bandage, my mom used to be on a nitroglycerine patch and had a reaction to the glue/bandage material. Thankfully we were able to place it on a different spot each day so that helped.
Do you have an option to try a different type of covering, perhaps one without an adhesive? If not you could try strategies to reduce the stickiness of the bandage, perhaps moisturizing well before applying?
If you think the problem is an allergic reaction be sure to clean the area well after removing the bandage and try a little hydrocortisone ointment.

Why does your mom need a large bandaid on her thigh at night?

Most seniors I know have extremely delicate skin, especially unexposed areas such as the thighs. Have you tried bandaid that are specially made for delicate skin?