I have a birth mark since I was born on the left side of my head mid top to front and on the side. There use to grow hair on this birth mark (thicker than on the right hand side). However since from the age of 17/18 years old it started falling out. On the right side of my head and on the back i still have a lot of hair. still have a lot of hair. The bald spot in the picture use to be fully covered. What causes this hair loss? And can I get a transplant?