There are MANY reasons why your cat might stop eating.  The following is a list of some of the causes of cat to stop eating.  Cats are very sensitive, therefore each cat may have their own unique reason that isn't on this list.  Regardless of the reason, if your cat stops eating for more than 48 hours, please take him/her to the vet.  Doing so will hopefully prevent them from acquiring Feline Hepatic Lipidosis and/or catch this condition in the early stages so that his/her life can be saved. 

Causes

A virus that makes the cat nauseaus or that causes a loss in a sense of smell/appetite.  Cats can get cold/flu like illnesses just like humans which can also go undetected. 

An underlying medical condition that causes discomfort or pain.

Environmental Stress:  moving to a new residence, having work done on the home, thunderstorms, fireworks, hot weather

Emotional Stress:  new baby, new pets, depression, owners going on vacation, death of another animal within the home 

Stale food.

An alpha cat that keeps others away from food.

Injuries sustained from a cat fight or an accident.

Bad teeth and gums.  

Hairballs. 

Medication (the stress of being given medication AND medication that causes nausea)


Symptoms 

If your cat stops eating, it is only a matter of time before he/she will begin to develop Feline Hepatic Lipidosis, also known as Fatty Liver Disease.  The symptoms of this start out slow and may not be noticeable.  They include:

*early stages

Lack of appetite

May go to food dish, but won't eat or picks up food in mouth then drops it back into food dish

Refusal to eat

Nausea

Lethargy

Vomiting clear and yellowish/green fluids

Depression

Change in sleeping habits

A tendancy to avoid and hide from family


*later stages

All of the above symptoms listed in early stages in addition those listed in later stages below:

Drooling

Semi-coma/coma

Blood tests will show elevated liver enzymes

Blood tests may show elevated bilirubin

Anemia due to red blood cell destruction as a result of liver malfunction.  This can also be seen as pale gums. 

Yellow eyes and skin (jaundice).

Extreme weight loss

Extreme weakness

Doesn't want to be touched or petted

Blindness