Hi.
Thanks for your query.
Noted the history about your 79 year old friend who is on blood thinner and develops huge swelling on her hand several times without hitting the hand on anything, X-ray is normal.
The commonest cause of such an occurrence without any
injury is
angioneurotic edema.
No one knows why this occurs.
Hence the treatment is always empirical in the form of a long term antihistamine, oral
steroids in tapering dosages, an anti-helminthitic for the worms in the intestine.
Try to identify the causes in the form of foods, beverages, scents, fumes, molds, fungi and anything.
There is a saying : Anything under the sun including the sun can cause an
allergy.
Also to get the investigations of the blood, stool, urine, X-ray of the chest and
ultrasonography of the abdomen.