What Is Causing My Hamster’s Fur Loss?

The cause could be nutritional, a problem with the endocrine system, a symptom of a systemic illness, or a parasite or fungus.

Running up against the wall of the wheel could cause fur loss. Khmel/iStock/Thinkstock

By Martha Boden


We have an adorable Syrian hamster, Peco, who’s about 16 months old, according to the rescue we adopted him from. He always was – and still is – the picture of health. He’s friendly and alert, has a great appetite and comes out every night to play when we call his name. We’re concerned because he seems to be missing two small patches of fur on his flanks, one on his left rear thigh and the other on the right side near the middle of his back. He doesn’t seem to mind, but we’re wondering what it might mean and what do to about it. Thanks for all your advice!


Thanks for writing! Your question is a great one and something that many hamster owners experience. Fur loss can be the result of a variety of factors, and sometimes these combine. The cause could be nutritional, a problem with the endocrine system, a symptom of a systemic illness, or a parasite or fungus.

Parasitic Infestation

I want to discuss the parasite issue first, because it is fairly common and there are some clear indicators as well as solutions. I have to emphasize that an experienced veterinarian can diagnose the cause with great accuracy, and provide a cure. Therefore, I’d recommend doing a bit of searching to find a veterinary clinic that works with small pets as soon as possible, and having Peco checked out. It can’t hurt, and I am hearing of more and more veterinary clinics that are knowledgeable about rodents and other small pets.

Just a brief digression here: All veterinary doctors will do their best to help a pet in need; it’s what they’re trained and motivated to do. But if they have no experience dealing with hamsters, their ability to help may be limited. When dogs and cats lose fur it may also be due to the problems outlined above, but there are a variety of other causes, and the treatments involved may be suitable for those pets, but not for hamsters. So please seek a vet versed in treating hamsters. And I’d advise all readers to do that research before there is a need, so you’re not dealing with a crisis and searching for a solution at the same time. That’s stressful and may eat up valuable time for you and your hamster.

Parasitic infestation can be scary and distressing for the pet and for you, but thankfully, it’s relatively easy to diagnose and treat. Look at Peco’s skin where the fur has vanished. Depending on his coloration, the skin should be clear, smooth and pinkish. If the skin looks healthy, clean and supple, it’s still best to seek medical attention, but it is less likely to be a parasite. If the skin is ruddy, raw and irritated-looking, or if there are bumps or scabs — and especially if your hamster is fussing and pecking at the area a lot — it may indicate the presence of a parasite. The most common parasites among hamsters are mites, which appear in two main forms, demodectic and sarcoptic (the latter are also called scabies mites). Both are bad, but the sarcoptic type may be somewhat more destructive and harder to fight. Slightly less common, but no less of a problem, are lice that can also attack small pets.

If you suspect parasites, the first and most important thing to do is to segregate the hamster’s dwelling from those of other pets, and always observe stricter rules of hygiene than usual when dealing with him. In other words, be aware that these parasites are constantly looking for a host, and can be conveyed through contact with clothing and supplies. So make sure the pet in question is as isolated as possible, and that you wash more thoroughly than you normally should when dealing with him for the time being. Your veterinarian will treat your hamster for parasites with medicines that go into his bloodstream to make the internal environment hostile to them. If the vet is experienced, she’ll know exactly how much medicine is needed, and in what doses, so as not to harm your pet while doing in the intruders. The treatment may require an injection of medicine, or oral administration, or a combination of the two, depending on the type of parasite and the severity of the infestation. There are also effective topical treatments. Follow your doctor’s advice and drug regimen precisely, and your hamster will get on the road to recovery, and hopefully fur restoration, right away. Sometimes the fur doesn’t grow back completely, but at least your hamster is rid of nasty, uncomfortable pests!

This goes without saying, but if there’s been a parasitic infestation, you’re going to have to toss all the potentially infested items in the hamster’s dwelling, and scrub his environment thoroughly with a pet-safe detergent and bleach. Be sure you’ve done your absolute best to rid the hamster’s environment thoroughly of pests.

Fungal Infection

Another cause of fur loss is fungal infection. The treatments vary for this as well, and may also include intravenous, oral or topical medication. An experienced veterinarian can diagnose the cause and advise accordingly. If you suspect either kind of problem, don’t attempt to treat it yourself with over-the-counter remedies. Most of the time when people do this they end up wasting time and money, and the problem becomes worse. You never want your pet to suffer unnecessarily.

Systemic Illness

If neither infestation nor fungal growth is the problem, there are some other telltale changes in skin texture or appearance that may indicate systemic illness. If the skin is very dry and flaky, and especially if the hamster is drinking a great deal, it could indicate an illness that is treatable if caught in its early stages. Similarly, if it is very wrinkly, bloated or loose, but not red or raw, the cause may be an illness that is causing an organ to malfunction. Sometimes such ailments are irreversible, but controllable. The only way to ensure a chance is swift and proper diagnosis by a professional.

Hormones And Nutrition

If none of these things seem to be a problem, if the skin looks clear and unbothered and the hamster’s overall behavior is normal – no picking, scratching, excessive thirst, or whatever – then the problem could be either hormonal or nutritional. If the fur loss is hormonal, there’s often nothing to be done because it may be an inherited trait, destined from birth, and so fundamental to the hamster’s makeup that it that it has no practical effect on his life or behavior. In those cases the baldness doesn’t spread quickly, I can happily report. When it happens to people, we wear wigs, or in some cases get surgical hair replacement. Unfortunately, neither would be an option for Peco. But I’m also happy to say that in some cases, as the hamster passes through various stages of life and metabolic changes take place naturally, such as passing beyond the childbearing stage for females, the fur may return as fully as before.

The nutrient cause is difficult to address with accuracy because we don’t really know precisely what nutritional deficits contribute to fur loss. Also, unless we’re hand-feeding our hamsters we can’t be sure what’s being eaten except after the fact. I’ve touched on diet before, but for now, suffice it to say that your hamster’s diet should include what is called a “lab block” or similarly potent and nutritionally comprehensive food. Unlike a mix, lab blocks and similar products contain a very wide complement of ingredients that ensure a balanced array of vitamins and minerals. I don’t recommend a diet solely of lab blocks, but including them or emphasizing them from time to time as your hamster’s main choice of food is a great way to achieve a balanced diet. And never underestimate the importance of some fresh foods daily. Hamsters are delighted by fresh foods, and their nutritional value is amplified by their digestibility. A remedy that is worth trying is nutritional yeast.

This is not brewer’s yeast, but a form that is sold for people as a type of vitamin supplement. It’s very well-known to those who enjoy smoothies. It’s filled with nutrients, including B vitamins and amino acids, and it’s pretty tasty. Just put a “pinch” over your hamster’s food every day for two weeks. You get best results by sprinkling it on foods like tofu or an apple chunk because those are moist, the yeast powder adheres to them and few hamsters can resist apple or tofu chunks. Yeast is strong stuff, so after two weeks, feed it every other day for a week, then taper off to twice a week, once a week and stop. In my experience, when this works the fur starts to return during that first two-week period, and plateaus in the third and fourth. Beyond that the yeast will cease to have any effect and may be more of a vitamin infusion than your hamster needs.

Rubbing Against Side Wall Of Hamster Wheel

One more potential cause of patchy fur loss bears mentioning. Many people report to me that their hamsters have lost a spot of fur, often around the rear flank or thigh, and often only on one side. It’s easy to overlook, but you should always watch how your hamster runs in his or her wheel, and pay attention to the way he interacts with his furnishings. In the midst of an enthusiastic run, for example, your hamster certainly won’t notice that he’s repeatedly rubbing against a side wall of the wheel, or the axle, and that may simply be pulling fur out by the root! This seems like something that ought to be obvious, but these are the kinds of things we overlook in our anxiety over disease or infestation.

That covers all the basic scenarios, and they all begin with properly identifying the problem. If you go through all of this with Peco and he still hasn’t regained his fur, just remember to give him more plain white tissue paper as an extra blanket when the weather is chilly, which is important. It’s also important that however funny-looking his fur loss may make him – I’ve seen healthy hamsters go pretty much bald, and it’s a startling look – he’ll always be the same loving, playful fellow, and your affection and attention will still be miraculous medicine that a veterinarian can’t supply.

Good luck!

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Critters · Hamsters