It was pointed out to me recently that when I'm having a foot pain flare, my feet turn bright red. (yes I am oblivious enough to have never noticed this myself)

I did a search for redness here and found a post from mrsD talking about magnesium, which I'm already taking. What I'm wondering is could the redness possibly be an indication of an allergy? And if it is, what kind would specifically cause redness on the feet?