Reasons for hard bumps under the skin of cats’ necks:

1. Generally, when a cat gets an injection, the doctor will choose a location near the cat’s neck. Therefore, if your cat has recently been vaccinated or injected, it may be that the drug has not been fully absorbed, or it may be a normal rejection reaction of the skin.

2. After a cat gets a skin disease, red and swollen patches will also appear on the skin. Cats generally feel very itchy and often want to scratch.

3. If the cat is infected with parasites or is bitten by mosquitoes, it will also cause skin infection and form a hard pack under the skin.

4. If it fights with other cats and is bitten, or experiences other trauma, the epidermis will heal without disinfection and sterilization, and the subcutaneous tissue will be infected with bacteria and inflamed, forming a hard bag.

5. If there is a hard lump under the skin of the cat's neck, it may also be a tumor, such as lipoma, lymphoma, skin hyperplasia, etc. It is necessary to go to the pet hospital for further examination to confirm the diagnosis.

6. It may be swollen lymph nodes in the neck. You can take heat-clearing and anti-inflammatory drugs.