Blood blister on leg age 68.

“No apparent cause .”
A doctor needs to see it .

I had this happen on my arm and it itched. Went to my doctor and he removed it. Not cancerous.

We don't know. WE aren't doctors and if we were, we would need to examine your loved one. This could be ANYTHING. It's most likely a scrape injury, but your loved one should be seen by medical. Just to let you know that my 85 year old brother died of sepsis from a tiny wound on his shin. The skin of elder's is very fragile and prone to injury. Usually there is healing without consequence, but these things can't be ignored.

Please provide more context: Is this person in a facility? Has dementia or other health issues? At home? Are you the caregiver? There's no way to provide suggestions without more details.