Hi there,
I had cellulitis on my leg from an insect bit in 2004 and ended up needing surgery to remove the resulting cyst which was about the size of an egg. I had circles of concentric cellulitis around the cyst and was on several anti-biotics after discharge and IV anti-biotic during admission to hospital. I was asked if I was diabetic as my glucose levels were a bit high.
Now if I get stabbed by thorns as I was 10 days in the garden I tend to develop these welts and resulting swelling. I did a homemade poultice of fullers earth, a face pack mixed with the powder of amoxillcillin capsules I had in the house. And then wrapped my leg in a bandage soaked in TCP. I went on amoxicillin immediately and carried on with the skin applications. I alternated with stuff called Sulfur 8 which is a sulfur based scalp ointment but is handy for folliculitis and infected bites. After five days I managed to get the welt down and avoid more surgery. So taking care that your legs are protected when there are bugs about, and from animal fleas and thorny plants is important.
I think getting checked for hypoglycemia, diabetes and other metabolic disorders might be useful. Cutting back on sugar and sugary fruits, might be prudent as well. Increasing Vit C for a while would probably be helpful.
The swelling: you might have something called Lymphodoema
http://209.85.229.132/search?q=cache:2Ap_hkXQBJcJ:medical-dictionary.thefreedictionary.com/Lymphodoema+lymphodoema&cd=4&hl=en&ct=clnk&gl=uk
this can be treated by a specialist who can help drain down some of the fluid, but see a doctor first to discuss.
All the best,
Adelaide