Like many other carnivores, ferrets have scent sacs near their anus. Secretions from these are used in scent marking. It has been shown that ferrets can identify whether such a mark was left by a male or a female ferret, without recognizing the individual. Like a skunk, a ferret can release this scent when startled or scared, but the smell dissipates rapidly. Most pet ferrets in the US are sold with these anal sacs removed, although this does not affect a ferret's natural musky scent. To eliminate this scent entirely, desexing is required, since it is through this odor that female and male ferrets find each other during the mating season.

Adrenal disease

Adrenal disease, a growth of the adrenal glands that can be either hyperplasia or cancer, is most often diagnosed by symptoms like unusual hair loss, increased aggression, and (in the case of females) an enlarged vulva.

Treatment options include surgery to excise the affected glands, melatonin implants, steroids and/or hormone therapy. The cause of adrenal disease is unknown, but speculated triggers include unnatural light cycles, diets based around processed ferret foods, and the premature desexing of pet-store ferrets. Others have suggested that the problem is hereditary.

Insulinoma

Ferrets are also known to suffer from insulinoma, a cancer of the pancreas. The growth of cancerous nodules on the lobes of the pancreas sometimes, but not always, leads to an increase in the production of insulin, which regulates the rate at which the ferret's body metabolizes blood glucose. Too much insulin will cause blood sugar to drop, resulting in lethargy, seizures, and ultimately death. Symptoms of insulinoma include episodes of lethargy, drooling, pawing and/or foaming at the mouth, staring "blankly" into space, and seizures.

Like adrenal cancer, the exact cause of insulinoma is unknown. It is speculated that the diets of domestic ferrets are too far removed from the natural diets of their polecat ancestors, and include too much sugar or simple carbohydrates.

Lymphoma

Lymphoma/lymphosarcoma is the most common malignancy in ferrets. Ferret lymphosarcoma occurs in two forms -- juvenile lymphosarcoma, a fast-growing type that affects ferrets younger than two years, and adult lymphosarcoma, a slower growing form that affects ferrets four to seven years old.

As in humans, ferret lymphosarcoma can be treated surgically, with radiation therapy, chemotherapy or a combination thereof. The long-term prognosis is rarely bright, however, and this treatment is intended to improve quality of life with the disease.

Viral diseases

ECE (epizootic catarrhal enteritis), is a viral disease that first appeared in the northeastern US in 1994, is an inflammation of the mucous membranes in the intestine. In ferrets, the disease manifests itself as severe diarrhea (often of a bright green color), loss of appetite, and severe weight loss.

Waardenburg Syndrome

Ferrets with a white stripe on their face or a fully white head, primarily blazes, badgers, and pandas, almost certainly carry a congenital defect known as Waardenburg syndrome. This causes, among other things, a cranial deformation in the womb which broadens the skull, causing the white face markings but also partial or total deafness. It is estimated as many as 75% of ferrets with visible Waardenburg signs are deaf. Beyond that, the cranial deformation also causes a higher instance of stillborn ferret kits, and occasionally cleft palates. Because of this, many breeders will not breed Waardenburg-patterned ferrets.