What Causes Swelling In Feet And Legs Of A Lung Cancer Patient?

my husband has non small cell lung cancer and has been in a clinical trial on Keytruda and Alimta for about 8 rounds. Once every 3 weeks. He is in the hospital now with severe swelling of his feet and legs and now the skin is blistering and peeling flaking. All doctors consulted agree that it is an allergic reaction to the cancer drugs. He has been on steroids for a few days( as a temporary ) measure to give him some relief. The wound care nurse recommended vaseline as a topical. Any other ideas for the cause or relief. Skin is bright red to purple mostly on legs but some on hands and arms too. Other complications are very low hemoglobin and platelet counts. Any suggestions.