I Have Been Using Diclofenac For Approximately 3 Months And

I have been using Diclofenac for approximately 3 months and within the last 2 weeks have developed a rash 2 quarter sizes on my rear hip where I have been using the ointment for arthritis in the right hip. I know a few years ago I used it on my knees and got an rash on just the right knee. Is there an allergy reaction to this product? YYYY@YYYY Thank you