The lupus rash is aggrivated by the sun. Does your worsen after you've been in the sunshine? Read the sticky at the top of this thread titled "Criteria to diagnose lupus". It's very informative. Just the rash isn't diagnostic. If you have 4 or more of the 11 common symptoms, it's likely. From my experience, my mouth ulcers were so tiny and painless that my dentist found them. That was my 4th symptom match - bummer!
There are rashes that look similar to ACLE = acute cutaneous LE = the rash associated with systemic lupus. Rosacea is one I know of.
Like Barbara H. just said, the rash associated with lupus is just one of 11 symptoms/criteria, and you have to have 4 in your medical history to be Dx'ed with lupus. So if you have a facial rash + some other things going on---things that occur frequently in lupus---that would add a lot of weight to a dr's opinion about the rash. And he/she should start looking quite a bit further than your face, I might add...
There's a "sticky post" at the beginning of the board listing the 11 standard criteria drs. use to Dx lupus.
If you use your broswer to look up "ACLE rash", you'd find articles describing the appearance, etc. plus pictures.
I knew I had a site on ACLE rash marked as a "favorite".
Here is a more complete list of things other than ACLE that can cause a red face: seborrheic dermatitis, photoallergic/phototoxic demratitis, polymorphic light eruption, acne rosacea, dermatomyositis, and drug reactions.