Ideally hair grows back spontaneously once cradle cap is treated as it does not destroy the hair follicle. Use of steroid
lotion like mometasone
along with minoxidil
solution would help in speedy hair regrowth if follicles are intact but if in case the condition was very severe and inflammatory very rarely it may cause scarring or permanent loss of follicles in such cases nothing would work. I would advise you to meet a dermatologist
nearby to get the area examined so that a proper treatment protocol can be suggested.
Hope that solves your query.