A "flare up" simply put means that a person is having lots of Lupus symptoms with blood work (sometimes)indicating that Lupus is active. A flare can include things like kidney inflammation, eyesight problems or even things as simple as an increase in fatigue etc.
Flares can be triggered by many things such as stress, infection, lack of sleep/rest etc. To get out of a flare, we usually get put on Prednisone (which is a steroid) to help calm down the immune system which when we are in a flare will be working overtime, attacking itself!
Flares are not fun, and some people stay in one for a few years!! I have been in one for 2 years, and hope that soon I will be better again. Hope this helps!