something strange and scary, please help! dog advice

sweetteaaa

Okay, my dog lexus was a rescue dog, and we've had her for over a year. Throughout that year she would swell up around the face area, like today, her right eye is swollen shut. We feed her dog food and water and she steals our free range eggs sometimes, nothing else. Does anyone know what might be causing this? Anything that can help? I told my mom that maybe an anti-inflammatory herb in her food would help, but I don't know what dogs are allergic to or and what not. Any suggestions?