If you look on the internet and magazines there are many people who claim to be 'skin experts' or 'dermatologists' and currently there is no law or regulation governing who can use these titles. In the medical profession in Europe to acquire full accreditation of the medical board of the country as a true specialist in skin disease doctors must go through rigourous training and exams. This is combined with many years of practical training.
In the UK a board certified dermatologist is known as a Consultant Dermatologist and will always be listed on the General Medical Specialist register which is found here
Further information on training in other European countries will appear here shortly.