Are skin problems easy to diagnose, or is there a lot of room for error?

Derms know! If you are seeing a dermatologist, the vast majority of skin problems are relatively easy for us to diagnose, as we see them all the time! there are of course always tricky problems, because rashes and skin lesions can vary depending on how long they are present, if infected, the skin type, prior treatment, etc. Sometimes even a biopsy won't give us the exact answer, but that's usually rare.