My Mother was scheduled to be released from rehab today when they noticed a huge red blotch on top of both of her feet.  They ruled out allergic reactions to meds as as well as infection.  She is taking Lasix for fluid retention in her feet and has been wearing compression stockings.  Any thoughts would be appreciated.
Go for liver function tests, bleeding tests, clotting test. Look for other similar lesions over the body. Especially joints. Ask history of any injury, or similar episodes of such lesion in response to trivial trauma.