For about the last 6 months, I've noticed that when I bump my arm or scrape it (not dramatically), I get a large spot on my arm or hand that looks similar to a blood blister but no blister Its always the shape of the scrape. I've also had times when I feel itching or burning and one will appear on my hand. They usually go away in a few days, but are very embarrassing. What could be causing this? I am 50 years old and the only medication I take is lexapro.