A friend with MS has been telling us about this fairly obscure symptom she has, and she ran across this potential cause recently:
"Most cases of Erythromelalgia (EM) are idiopathic (cause unknown). Sometimes EM is secondary to other medical conditions including autoimmune, neurologic or blood disorders. Lupus, polycythemia vera and multiple sclerosis
... symptoms may include hands or feet that are very red to purple in color, are perhaps swollen, hot to the touch, and have burning pain.
... symptoms may appear in the face, ears, knees or other parts of the body.... Some notice a continual burning pain while others are troubled with "flare-ups" or episodes lasting from minutes to days in length.
... flare-ups are provoked by heat and exercise, and symptoms are relieved by cooling and elevating the affected extremities. Some TEA members have found that foods, spices like MSG, beverages (particularly alcohol) and some drugs can make symptoms worse."