What dept would be best to get a recheck for head lice to be sure its gone? dermatology?

You should be able: to look at home to make sure the nits/lice are gone. If you're not sure, then call your own doctor (if for your child, their pediatrician). If you're a teacher, or if this is for your child, the school nurse can help.There are also professional "nitpickers" who just deal with lice and getting rid of lice. A dermatologist is not necessary for this.

Head lice: Many services are familiar with diagnosis of head lice. General practice / family doctors and, school nurses have a lot of experience in head lice management. They will be looking for live lice and for brown egg cases near the scalp as well as blood spots behind the ears.

Head Lice: If you need help to determine absence of lice and nits- your pcm would likely be fine.