Allergy reaction can cause swellings and is also seen in people who have urticaria + angioedema. But usually for allergic reactions, there will be other symptoms that comes along... itching, hives. Chronic urticaria is a condition where some patients will have hives and angioedema(swellings) too. However, it is not an allergy but more of an underlying problem which can range from infection to serious problems like cancer(not so common though). There are people who have found that their chronic urticaria is related to their thyroid problems. And when they got their thyroid under control, their hives got better and so does the angioedema. But I don't know if CU could be causing your swellings since you didn't mention hives.
For patients with heart or kidney disease related edema, the doctors give them diuretic(sp) to help with water retention.
Have you have any blood test for autoimmune disorders(lupus, rheumatoid arthritis...etc)? They can cause swellings too. Where do you get swellings other than ur legs and feet? How long do the edema last? Are your doctors doing anything to help with the edema?