The answer is dermatologist. Dermatologists specialize in skin care and what not.
Answer:
there are many different nutrients our body can't produce, such as: omega-3,
vitamins, and minerals, just to name a few. But, I feel water would be your best answer. Yes, I know, surprising, but true.
A skill related is fitness including training to improve speed, balance, coordination, power, and finally reaction time.
Hope this helps...