What Causes Choking While Swallowing Food?

At the age of just under two, my child choked on some food. She was discolored and unable to breathe for several minutes. She is now six and any time she plays or gets even slightly hot. the right side of her neck and right upper chest gets a red/purple blotchy discoloration. The discoloration covers a large area considering her overall size. It takes several hours, once she rests, for this to go away. The other morning she woke up with it....I guess she got hot during the night. She seems fine, but I can't help but worry that this is a vascular malformation ( or some other abnormality) caused by the choking that may result in problems for her later in life. It is very prominent and easy to see. People always ask about it and become concerned for her. It's size or frequency has not lessened over the years. To see it causes concern and worry. What is this? I have asked several doctors, but do not get an answer. They just kind of shrug. If I knew what it is and why it happens, it may ease my mind. I would be very grateful for an anwer, even a hypothesis. Stephanie Poole(RN)