Hamster balding spot on his head

Question
QUESTION: Hi my name is Lexie :) I got my hamster, Max, last April. So maybe he's around 4 months old. A couple of days ago I found a dark spot on his head, right between his ears. I thought it was a dark pigmentation on his skin, but upon closer inspection I realized that it was a balding spot. The spot only had short 'under' fur. He is umbrous, so maybe that's why it looks dark? I also noticed that the area around his eyes also only consist of short fur, but this looks more cinnamon-red rather than dark.  What could it be?? I cant help but worry. :((

Added info:
His water has vitamins, and his diet consists of commercial food mix of grains, cornflakes, sunflower seeds, oats and nuts (he ignores the pellets completely!), he has a wheel that he uses regularly. His behavior has not changed, the rest of his body is healthy and furry.
He likes playing with his bottle so it does leak and was completely destroyed 2 days ago.
I use recycled paper pulp for bedding.

Thank you so much for your time :)

ANSWER: Hello Lexie,
I believe I found the answer to your problem near the last line of your question. Leaky water bottles are often the culprit of fur-loss in otherwise healthy hamsters. Look for a water bottle with a tight seal where the spout screws onto the bottle, and make sure the ball at the end of the spout isn't too loose. Also, too many seeds and grains can cause fur loss, a problem easily remedied with fresh vegetables. Many people think that hamsters can only eat nuts, seeds, and grains, when, in reality, they can eat many of the foods their owners eat. The only foods that should never be fed to hamsters are any kind of citrus fruit, sugar (or anything containing high amounts of sugar since hamsters are susceptible to diabetes), and too many fruits or vegetables with high water content (they can cause loose stool). The best vegetables to feed hamsters are carrots, broccoli, lettuce, and cabbage (I have found that carrots and broccoli are a favorite.) Just put a few pieces of vegetables in his food dish in the morning (about 3 days a week) and remove anything uneaten by the end of the day. Peanuts and peanut butter are also a good source of protein and a favorite hamster treat!

Good luck,
Devin

---------- FOLLOW-UP ----------

QUESTION: I think it might have gotten worse today. There is a noticeable loss of fur around his eyes as well. Do you think this is still caused by too much grains/leaking water bottle? I've fixed both problems by the way...around how long before i expect his fur to grow back? I appreciate your time so much! Thank you!

Answer
Since that hasn't worked, there are two different treatments for general hair loss: 1) one or two drops of cod-liver oil daily; 2) crush a yeast tablet (without garlic, which is hard on hamsters kidneys) in top of the food for three or four days, then decrease to once a week. If that doesn't work, he needs to see a veterinarian.

-Devin