3 doctors weighed in:

Why do some people have birth marks?

3 doctors weighed in
Dr. M. Christine Lee
Dermatology
1 doctor agrees

In brief: No one really knows

Nobody really knows what causes birthmarks.
Vascular birthmarks are not hereditary but thought to be caused by overdevelopment or overgrowth of blood vessels. Many theories for different types of birthmarks: some may be hereditary (most are not), some caused by random genetic mutations, overgrowth of pigmented cells called melanocytes, abnormal collection or overgrowth of blood vessels.

In brief: No one really knows

Nobody really knows what causes birthmarks.
Vascular birthmarks are not hereditary but thought to be caused by overdevelopment or overgrowth of blood vessels. Many theories for different types of birthmarks: some may be hereditary (most are not), some caused by random genetic mutations, overgrowth of pigmented cells called melanocytes, abnormal collection or overgrowth of blood vessels.
Dr. M. Christine Lee
Dr. M. Christine Lee
Thank
Dr. Thomas Fiala
Surgery - Plastics

In brief: Random luck

In most cases. Occasionally, there are birthmarks that are associated with genetic syndromes, but these are less common.

In brief: Random luck

In most cases. Occasionally, there are birthmarks that are associated with genetic syndromes, but these are less common.
Dr. Thomas Fiala
Dr. Thomas Fiala
Thank
Read more answers from doctors