I Have Red Circles That Appear On My Body Different

I have red circles that appear on my body different sizes if you scratch the surface it has a very thin tissue paper skin if you repeat scratching it it gets bigger redder and forms a scab. I have had one looked at by a skin specialist but he doesn't know what it is can you help me?This has been going on for about 20 years and rarely only once on my head mainly from the head down. Connie