Why Does My Cat Throw Up White Foam?

The reasons for throwing up:
1, stomach diseases
Chronic gastritis, pyloric obstruction, cancer, parasitic diseases (soaked wing nematode genera, uaroo nematode genera), dietary irregularities, or overeat, eat into the grass or indoor plants, fresh into the hair ball
2, abdominal disease
Inflammatory bowel disease, pancreatitis (chronic), peritonitis, liver diseases (hepatitis, bile duct, liver fat deposition), intestinal obstruction (complete obstruction or partial obstruction caused by linear foreign body), tumors (stomach, pancreas or intestine), colon diseases (colitis, Hirschsprung's disease), parasites
3, systemic or metabolic diseases
Uremia, drug or toxin, such as paracetamol, tetracycline, doxorubicin, digoxin, etc., ketones disease, evil immitis, hyperthyroidism .
You'd better go the the Veterinary Hospital.

I'm not so sure because I'm not a doctor but your cat could most likely have a infection of the throat or stomach.

He could be throwing up, because my cat did that two or three times. I hope your cat gets better. Peace. :)