The reasons why a hamster has a big swollen neck:

1. If the breeder feeds the hamster high-calorie food for a long time, it may cause the hamster to have a big swollen neck. It is caused by high-calorie food causing hamsters to get angry.

2. This is likely to be tumor proliferation. Hamsters are rodents, and rodents are highly susceptible to tumor diseases.

3. When a hamster is infected with a skin disease or bitten by an insect, pimples, itching, and hair loss will appear on the hamster's skin.

Solutions to a big swollen neck of a hamster:

1. The breeder can stop feeding the hamster high-calorie foods, such as peanuts, etc., and then the breeder can Choose to feed your hamster only food or fresh fruits and vegetables to ensure a balanced nutrition for your hamster. The bumps on your hamster's neck will disappear quickly.

2. If it is a tumor, the breeder needs to take the hamster to the pet hospital immediately for a x-ray to confirm the diagnosis, and further targeted treatment to prevent the condition from worsening due to delay.

3. If the symptoms are caused by skin disease, the breeder needs to clean and disinfect the breeding environment as soon as possible and take the hamster to the pet hospital for treatment in a timely manner.