Hi JncChr:
The lining of the mouth is one of the most common targets in lupus and present as sores or lesions in the mouth (usually on the inner cheeks and the roof of the mouth) and can be seen as lip lesions which can become ulcerated and painful. They resemble red plaques surrounded by lacy whitish areas.
Herpes simplex labiallis (fever blister) is common in normal people and can be triggered by lupus symptoms (infections, stress, sun exposure). Lupus patients who are receiving immunosuppressive drugs tend to have these break outs more oten (every month) and they tend to last longer than three weeks. The best treatment is to lessen the exposure to immunosuppressive drugs and to use corticosteroid-sparing drugs (like azathioprine, mycophenolate mofetil, and cyclophosphamide). However, discuss any changes in your drug treatment with you doctor thoroughly as you may have other symptoms and treatments which must be considered!
I Hope That I Have Been Helpful 8)
Peace and Blessings