I have a friend whose face swells periodically and she gets a rash on her face. it swells so badly that her eyes cannot be seen as well as normally.

This : This is definitely not normal. You have not provided enough information to venture a suggestion as to the cause of the problem. I recommend an evaluation by their physician. The problem sounds like an allergic reaction so the key is identifying the causative agent. Keeping a diary of when the problem occurs and what they have come into contact with or eaten would be valuable to the physician.