The reasons why there is a hard thing on the cat’s neck: 1. It may be that the bones at the back of the cat’s neck naturally bulge. 2. It may be caused by injecting drugs. 3. It may be that the cat was bitten by mosquitoes, causing the bumps. 4. It may be caused by tumors. 5. It may be caused by the cat being hit and enlarged.

What to do if there is a hard thing on the cat’s neck:

1. It may be that the bones at the back of the cat’s neck naturally bulge. There are naturally bones on the back of his neck, and the bones are naturally raised, so cat owners don’t have to worry.

2. It may be caused by injecting drugs. Usually subcutaneous injection is used when injecting drugs into the cat's neck. If the injection site is abnormal, the drug will be in the form of a hard lump. The cat owner can use a warm towel to apply hot compress to the cat.

3. It may be that the cat was bitten by mosquitoes, causing the bulge. If the bulge caused by mosquito bites is serious and you feel something hard is there, you need to take your cat to the pet hospital for treatment in time.

4. It may be caused by tumors. When a cat with a tumor will have a hard thing on the back of its neck, it is recommended to consult a doctor immediately and take a radiograph for examination and treatment.

5. It may be caused by the cat being hit and enlarged. If the cat is hit hard, it may cause swelling and hard objects on the back of the neck. It is recommended to take the cat to the pet hospital for examination and treatment immediately to avoid adverse consequences.