That's a bit of a sweeping statement! Perhaps that's true for you, but you cannot say that it's true for everyone.
From personal experience I can tell you that eggs and lean meats can never aggravate your acne. I have for some years now avoided simple carbs, sugars and processed foods and stuck to having eggs, lean meats, veggies and very little complex carbs and acne has stayed miles away from me.
Yes it is! There are people out there that are allergic to eggs and red meat. There is probably a post on here about someone eliminating those two foods from their diet and becoming clear. But, that isn't going to work for everyone because we're not all cut from the same cookie cutter.
I'd say the only way to tell if you're allergic to a food is if you go get an allergy test done. It's just the easiest way to find out. Then you don't have to go stressing out about what you can and cannot eat based on someone else's experience.
Some are lucky to find their triggers without medical help and others not too much.