My Dad Is 93 And Has Several Different Shape Blood

My dad is 93 and has several different shape blood blisters on his upper arm. I have seen this on several other elderly people and was told that because the elderly has such thin skin and the blood capillaries are close to the skin that they form probably from clothing rubbing across the skin, Is this what you think it is.. He wants to go to the Dr with this,, over time they disappear and then later on appear again.