Niacin-Like Reaction ???

I was wondering if anyone might have any ideas...
My 7 year old daughter has had 2 reactions in the past month.
She gets bright red all over her body, especially her ears and arms and is hot to the touch. She feels tingly.
She looks and feels just like I have in the past after taking niacin. She isn't really in pain at all, just a little uncomfortable because she is hot and her skin feels like it stings. This lasts for 45 minutes to an hour. Then she is fine. She does not actually get a rash unless the allover redness would be considered a rash.
The first time she did this, she was eating goldfish crackers which is normal. The second time she ate natural applesauce and a string cheese both of which are something she eats regularly. I cannot really see where this has any link.
She has complained in the past year or so about pain in her legs, especially at night and will occasionally wake up late at night crying because of it. Sometimes I passed it off as how she will sleep with her legs twisted to one side or curled up.
Now I am wondering about rheumatoid arthritis. I really should go and get some tests done.
My oldest daughter is now 14 and was daignosed about 6 years ago with JRA but has since been just fine. She has been to an opthalmologist and rheumatologist regularly and has had no problems except for an occasional sore ankle or a little pain depending on the weather.
I don't remember my oldest daughter having any reactions like this at all. I would not have even thought of this but my dad suggested it.

[txsilver]

Rashes can be associated with JRA. With leg pain, her sister being dx with JRA and the rash it is definitely time to get her checked.  You are on the right track.  Let us know what you find out.