What Causes Swelling And Redness On Legs Post Treatment For Bronchitis?

3 weeks ago, I was in hospital for bronchitis, exerbation of asthma. 2 days I to my stay of 4, my right lower leg became red swollen and shiny . Had an ultra sound. It was negative Dr put me on clandamycin. It went away in 3 days. I have been j me for 2 weeks. 2 days the same symptoms are back. I don t know why