Bald spots can appear when they are run down and the mites which live happily and naturally on their bodies overwork. Other reasons can be hormonal or even something like the spoke on the wheel rubbing against their neck when they run. What type of wheel does Gerald have? How much clearance does he have from the centre spoke, if it even has one
Have you changed bedding packets recently or opened a new bag of food etc. These can have mites in them and should be preferably frozen for 48 hours to kill them off after purchase. Do you have a magnifying glass? You may see black tiny dots if it is mites though different species are harder to see than others. Is the skin flaky or dry? Make sure to give some nutritional yeast and if the skin is dry maybe some cod liver oil drizzled on his food too would help. You know bottom line any health concerns should be referred to a prefessional and I know you will use your best judgement. Keep us informed on how he is doing please. Good luck Gerald - bald men are more virile they say though
Remember this post I made a short time ago?
"Vitamin B / Nutritional yeast
Hamsters eat their own droppings (called coprophagia), and this is thought to be important as a source of vitamins B and K. Sunflower seeds are also rich in B vitamins. B vitamins are good for hairloss and act on the nervous system and therefore also very good for reducing stress. Stress is the primary cause for many hamster diseases which is why it is also good to use a pro-biotic on a regular basis. Stress tends to lead to a disturbance in the hamster's digestive system, and the pro-biotic helps to encourage the growth of replacement good gut flora/bacteria. If you do wish to supplement your little one's diet with yeast a pinch a week of good nutritional yeast is sufficient. It can be found in health food stores and is better than baker's yeast as it is less bitter and therefore more palatable to our babies. Tablets designed for pets such as cats and dogs can be used, however make sure they are plain and don't contain any garlic as this has been found to be harsh on hamster's kidneys. A half a tablet a week should be fed if you decide to use this source of B vitamins."