Some parts of my dog's body has lesser hair?

So, I bought a puppy a while ago (5 months) and some parts of his body (right side of face, a part on his rear leg) has lesser hair than the other parts of his body. What could be the cause? Will it eventually grow? What can I do to make the hair grow?

I think its normal but take it to the vet to make sure.

If you don't get to the cause, there's a good chance more spots will creep up.Is he scratching? If he's itchy, likely causes would be mites, fungus, fleas, or allergies (something in the food or in the environment). If he's not scratching, fungus is more likely. There's a lot of possibilities. First thing I would do is put him on flea prevention and look him over good. Part the fur and look for black/brown dirt specks. If you see any of that, he has flea activity. If you don't see any of that, you should probably start at the vet. There are a lot of options and it can be tricky to track down, even with the help of experts.