My friend has had an allergic reaction on the arch of her foot due to the latex in shoes she has worn. This reaction has lingered for approximately 6 months. So, yesterday she gets this lump on the medial side of her foot around the malleolus. It feels warm and it hurts when she walks. What confuses me is that her joint does not hurt and it seems to shift in shape and size and it's red, but she can walk okay on it. Do you have any ideas about this one? She does plan to get into a doctor this week.