I have a daughter, age 4years 10 months. She is very active, healthyand happy kid. She eats healthy food(homemade), occasionally junk or outside food. All the vaccines are done as of now, next  one is on June 26. Vitamine D also I am giving as per pediatrician. She plays outside. She is exposed to the sun as well in the evening since morning she has school. The issue is, today, I have found one white hair about an inch rest length is black. I am worried about why it is happening to her at such a tinder age. What precautions can we take to prevent this? Any remedy apart from medicine.