The usual cause of vomiting in ferrets is a foreign body in the stomach or upper intestine. The most common foreign bodies are pieces of rubber that they have deliberately eaten, or hairballs from accidentally swallowing masses of hair during their molting (shedding) period.
Ferrets kept under natural light cycles shed their coats in late fall and spring. Particularly in spring, ferrets shed hair very dramatically. If they live in a home kept lighted until 9 o'clock or later every night throughout the seasons, their shedding periods will not be as predictable. They do groom themselves, more or less, depending on the individual, but they also pick up a considerable amount of loose hair from their bedding. Shedding ferrets can be brushed daily to collect as much loose hair as possible, and they can be shampooed once or twice weekly for the same purpose. Their bedding should be changed more frequently than usual while they are shedding, and the cage and play area can be vacuumed. These steps will reduce the chance that ferrets will get hairballs.
Not all ferrets with hairballs vomit. Some just stop eating, or eat very little, and pass thin, ribbon-like stools in very small quantities. If the stool is teased apart it will be found to contain a great quantity of hair. The treatment for this is simple and effective most of the time. There are many commercially available, palatable, laxatives (e.g., Doctors Foster & Smith Hairball Remedy, Laxatone) for cats, and a few for ferrets. These come in tubes like toothpaste, and can be fed directly from the tube, or dispensed along the edge of the ferret's dish. Most ferrets will eat any amount offered. To prevent hairballs, each animal should get about an inch of paste per day during its molting period.
To treat a ferret that does not appear ill, but is vomiting, or has suddenly stopped eating, or is passing thin stool as described, offer a couple of inches of paste several times the first day. If there is no improvement by the second day a veterinarian should see the ferret, which might have another kind of foreign body or another disease. If the ferret is better the second day, continue the treatment at a reduced dosage. This laxative can cause severe diarrhea if the ferret is allowed to eat all he wants, which might be the whole tube. Four or 5 inches a day is maximum for home treatment.
Ferrets with other types of foreign bodies might not respond much to the laxative treatment. Some ferrets, especially recently weaned kits, will chew up their cloth bedding, and a laxative usually relieves this type of blockage. However, ferrets love to chew any kind of rubber, especially baby bottle nipples and pacifiers, and this often will cause a complete obstruction that is life-threatening and will not be moved with laxatives. These ferrets become very sick overnight. They might not vomit more than once, but refuse to eat and become dehydrated. They look very ill, with half-closed eyes. A ferret in this state requires immediate veterinary attention. Surgery is necessary to remove rubber or other hard bits of foreign material from the intestine. Most ferrets recover from surgery very well.