Cats can pose genuine health risks to their owners, from allergic reactions and respiratory problems to infections spread through bites, scratches, and litter boxes. For most healthy adults, these risks are manageable with basic precautions. But for pregnant women, young children, and anyone with a weakened immune system, the dangers are more serious and worth understanding in detail.
Cat Allergies and Asthma
The most widespread health issue cats cause is allergic disease. Unlike most other mammals, the primary allergen cats produce is a protein called Fel d 1, found in their skin, saliva, and fur. When cats groom themselves, this protein dries on their coat and becomes airborne on tiny particles. It’s remarkably persistent: Fel d 1 lingers in homes for months after a cat has been removed and has been detected in buildings where cats have never lived, carried in on clothing.
For people sensitized to this protein, exposure triggers an immune response that can range from sneezing and itchy eyes to full-blown asthma attacks. Research has found that elevated levels of Fel d 1 antibodies in the blood are strongly correlated with the prevalence, severity, and persistence of asthma, particularly in young adults. In children, sensitization to this protein is considered a potential risk factor for developing allergic asthma. The allergen is especially effective at triggering reactions in the upper airways, and larger airborne particles can provoke a bronchial response at concentrations 20 times lower than smaller particles, meaning even casual exposure in a room with poor ventilation can cause symptoms.
Infections from Cat Bites and Scratches
Cat bites are far more dangerous than most people realize. While dog bites happen more often, cat bites become infected at dramatically higher rates: 20 to 80 percent of cat bites lead to infection, compared to 3 to 18 percent of dog bites. The reason is anatomy. Cat teeth are thin and sharp, creating deep puncture wounds that push bacteria beneath the skin and then seal over, creating an ideal environment for bacterial growth.
The bacterium most commonly responsible is found in the mouths of nearly all domestic cats. It’s isolated from about 75 percent of cat bite wounds, and cats account for 60 to 80 percent of all human infections caused by this organism. Symptoms typically appear within hours: rapid swelling, redness, and intense pain at the bite site. Without treatment, the infection can spread to tendons, joints, or the bloodstream.
Cat scratches carry their own risks. Cat scratch disease, caused by a different bacterium, produces swollen and tender lymph nodes one to three weeks after a scratch, often accompanied by a low-grade fever and a small bump at the wound site. Up to one in three healthy cats carry this bacterium in their blood, with kittens being the most common carriers. Most cases resolve on their own, but rare complications can affect the eyes, liver, spleen, brain, or heart valves. Children under 15 are the most frequent victims.
Cat saliva also harbors bacteria that can cause a rare but severe bloodstream infection if it enters an open wound or sore. This can lead to sepsis, kidney failure, and gangrene, particularly in people with compromised immune systems.
Toxoplasmosis: The Litter Box Parasite
Cats are the only animals that shed the parasite responsible for toxoplasmosis in their feces, making the litter box ground zero for human transmission. You can become infected by accidentally ingesting microscopic amounts of the parasite while cleaning the box or through contact with contaminated soil outdoors where cats have defecated.
Most healthy adults who contract toxoplasmosis notice nothing at all, or experience mild flu-like symptoms, swollen lymph nodes, and muscle aches. The real danger is to two groups. For pregnant women newly infected during pregnancy, the parasite can cross the placenta and cause congenital toxoplasmosis. Infected infants often appear healthy at birth but can develop serious eye damage, brain damage, or other organ problems later in life. For people with weakened immune systems, the parasite can cause severe damage to the brain, eyes, and other organs.
The mental health implications of toxoplasmosis have drawn increasing scientific attention. Multiple meta-analyses have found that people with schizophrenia are significantly more likely to test positive for past toxoplasmosis infection than the general population. Research published in Nature’s Schizophrenia journal found that infected individuals with schizophrenia scored lower on measures of global cognition, verbal memory, learning, and social cognition compared to uninfected patients. Higher concentrations of antibodies to the parasite correlated with worse negative symptoms and overall symptom severity. The parasite has also been linked to psychomotor impairments in people without psychiatric disorders, though research into how these effects work is still evolving.
Roundworms and Other Parasites
Cats infected with roundworms shed eggs in their feces, and these eggs can survive in soil for years. If accidentally ingested, typically by children playing in contaminated dirt or sandboxes, the larvae can migrate through the body and cause two distinct conditions.
Visceral toxocariasis occurs when larvae travel to internal organs, producing fever, coughing, wheezing, abdominal pain, and an enlarged liver. Ocular toxocariasis happens when a larva reaches the eye, causing redness, seeing spots or flashes, an abnormally colored pupil, and in some cases, permanent vision loss. It typically affects only one eye, which makes it particularly distressing when it strikes children.
Ringworm and Fungal Skin Infections
Cats, especially kittens and strays, are the primary carriers of a fungus that causes ringworm in humans. This is the most common animal-transmitted fungal skin infection and spreads through direct contact with an infected cat’s fur or skin, even if the cat shows no visible symptoms.
On the body, ringworm appears as the classic ring-shaped red patch with a raised border and clearing center, sometimes with itching, pustules, or small bumps. On the scalp, particularly in children, the same fungus can cause a more aggressive reaction: an inflamed, boggy, tender mass with pustules and swollen lymph nodes that can lead to permanent hair loss through scarring.
Higher Stakes for Vulnerable People
For people with weakened immune systems, the risks above aren’t just inconveniences. They can be life-threatening. The CDC notes that people undergoing cancer treatment, organ transplant recipients, those with HIV/AIDS, people taking high-dose steroids, and those with liver cirrhosis or a missing spleen may be advised to give up their cats entirely.
Those who choose to keep their cats are advised to take specific precautions: have cats tested for feline leukemia and feline immunodeficiency viruses (which don’t spread to humans but make cats more likely to carry infections that do), keep nails trimmed short, avoid rough play that could lead to scratches, and scoop the litter box daily since the toxoplasmosis parasite takes one to five days after being shed to become infectious. Pregnant women should avoid the litter box altogether if possible.
Putting the Risks in Perspective
None of this means cats are inherently dangerous pets for the average healthy person. Millions of people live with cats their entire lives without contracting any of these conditions. But the risks are real, and they’re worth knowing about, particularly if you’re pregnant, have young children crawling on floors, or have any condition that suppresses your immune system. Simple habits like washing your hands after handling your cat, cleaning bites and scratches immediately with soap and water, keeping cats indoors to reduce their exposure to parasites, and maintaining regular veterinary care eliminate or dramatically reduce most of these risks.