My wife has had an Ilia conduit operation 6 years ago & has a Stoma bag, crystals forming with burning sensation?

My wife has had an Ilia conduit operation 6 years ago & has a Stoma bag. She has a constant urine infection & has had to take antibiotics regularly as she has developed Kidney problems. Her urine is burning her flesh area around the Stoma and is causing crystals to form. She has been told to dab the area with white vinegar. A very painful experience every time, That area hurts all the time but however she has done this and after two weeks, they went. Very upset to see the crystals have returned after just two days. What else can she do to relieve the situation?
Thank you Doctor.