The reasons why kittens vomit mucus just four days after birth: 1. It may be due to catching a cold. 2. The kitten may be infected with feline distemper virus. 3. It may be due to prolonged hunger.

What to do if a kitten vomits mucus just four days after birth:

1. Newborn kittens are still relatively weak and can easily catch colds, leading to vomiting and mucus. In this case, it is recommended to take measures to keep the kitten warm, and use electric blankets, air conditioners and other items to help keep warm.

2. Kittens infected with feline distemper virus can also cause vomiting, which is usually accompanied by depression, decreased appetite, abnormal body temperature, etc. It is recommended to consult a doctor for medication.

3. It may be due to long-term hunger. If a cat has not eaten for a long time, excessive gastric acid secretion will cause vomiting of yellow water. It is recommended to feed the cat an appropriate amount of glucose or nutritional paste, and feed it regularly and quantitatively every day.