Had 4 laser hair removal treatments and I'm having second thoughts. Is it too late or will the hair eventually grow back?

Hi and thank you for your question! In general, approximately 10-15% of the hair follicles are destroyed during each session of laser hair treatment. Hence, after completing 4 sessions you are expected to have around 50% of the hair follicles intact. Do not be alarmed by the patchy hair growth now as it will get more uniform with time. Another factor that works in your favor is that hair growth in bikini area is regulated by hormones and new hair follicles are continuously made in this area. This is often a nuisance for patients undergoing bikini laser hair removal as they often need touch-ups every once a while with the new hair follicles growing, but in your case the new hair follicles will add more hair as time passes. Overall in long-term you should be fine. I hope it helps and good luck! 

You should be fine to switch from full brazilian to bikini line only hair removal after 4 treatments. The treated areas will probably have less hair than previously, but should look fine in a few months

Hairs follicles that have been destroyed already are permanently lost. However, with four treatments you still should have some growth in unaffected follicles as not all hairs are in the effective part of the growth cycle to be treated at each treatment. Additionally, you will develop new hairs throughout your lifetime, so you will always have some new growth there. Even the most effective laser hair removal only has 75% permanent hair loss. The rest will be thinner, less dense, and lighter in color, but they may still grow. "This answer has been solicited without seeing this patient and cannot
be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."