A hamster that scratches itself repeatedly with its back legs will be suffering from one of the following: dry skin, mange, mites, fleas, or some form of allergic reaction.
If the hamster’s ears are dry and look ‘flaky’, it might simply be a dry skin issue, a common symptom in warm, dry spaces such as houses (and one that humans suffer from too). You can help the condition by applying a little petroleum jelly to the back of your pet’s ears once a day. This should be enough to stop the itching and to keep the skin hydrated.

If a hamster is forever scratching itself, there’s an underlying problem
Does Your Hamster Have Mange or Mites?
Mange is another cause of itching in hamsters. Sarcoptic mange is brought about by an infestation of a certain type of microscopic mite. These cause the skin to become dry and irritated, until it becomes scabby and crusted. The mites themselves are not visible to the human eye unaided, so you need to look for the symptoms. The crust-forming critters burrow under the hamster’s skin, and the condition soon becomes very painful for your poor pet.
Treatment includes thoroughly cleaning the cage and purchasing Ivermectin drops from your vet in order to help fight the mite.
If your hamster has dry skin all over its body, with irritation to match, it could be down to non-mange mites. Mites are tiny invertebrates that live on an animal’s skin. In small numbers they are not much of a problem – but small numbers can very soon become large numbers! Once there is a major infestation it can get very uncomfortable for your poor pet. His skin will become crusty, and there may be some hair loss. A vet will prescribe medication treat the problem.
Is Your Hamster Allergic To Something?
Hamsters are sometimes allergic to something put in their enclosures, resulting in itchy and irritated skin. It could be a toxic wood or chemical from a handmade chew or toy, an item of food, or something in the house environment that disagrees with the hamster. (Then again, it may be due to fleas.)
Allergies can be dangerous if not diagnosed and treated. If the scratching is accompanied by issues such as wheezing, sneezing, difficulty breathing, or discharge from the nose or eyes, it is probably down to an allergy.
This doesn’t rule out the possibility that the hamster may be suffering multiple health issues. For example, itchy skin plus a runny nose and breathing problems could indicate a respiratory infection and mite infestation double whammy. A vet will be able to provide guidance and, hopefully, a diagnosis.
Karen, 18 April 2022
So, my hamster has been losing fur behind his ears and is itching a lot. I'm not sure what it is because he does not have mites, fleas, or dry skin. I would like him to live an enjoyable life and for him to feel comfortable. Please help me!!!!!!!!!!!!!!!