Unusual cat illness signs can include frequent attempts to vomit up a hairball, with no luck for the cat. Of course all cat owners are used to the occasional hairball being expelled. But you should check with your vet if no hairball comes out. A cough like this can possibly signal feline asthma, or something else more serious. Check with your vet to be on the safe side.
Vomiting can also be a sign of worms. Some worms are more dangerous than others, so again a trip to the veterinarian is advised. Attempting treatment yourself is not a good idea without knowing exactly what kind of parasite your cat is infested with.
To most good cat owners, it is obvious that illnesses should be promptly treated. On the other hand, this sort of thing can get out of control, and occasional vomiting can become more frequent without a cat’s human companion realizing. It pays to catch a cat illness early before it becomes something serious.