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Indoor Cats vs. Outdoor Cats: Health Problems and What Vets Think

Pay attention to signs that your cat needs immediate veterinary attention. Here are the top problems we see with indoor cats and with outdoor cats.

Indoor cats vs. Outdoor cats
Indoor cats vs. outdoor cats: Many people don’t agree that letting your cat outside is in their best interests. Photo: sspiehs3

Does your cat roam free outside? Maybe your cat is strictly indoor-only? Few topics polarize opinion more than the matter of indoor cats vs. outdoor cats.

One side is horrified that anyone would ever let their cats outside, given all the hazards (traffic, predators, disease, deeply disturbed cat-hating humanoids). The other side regards keeping cat indoors as akin to life imprisonment.

Indoor? Outdoor? Ultimately, each person must decide what makes the most sense for their cat.

In this 3-part article, you’ll learn about the health risks of indoor cats vs. outdoor cats so you can make the decision that’s best for your circumstances:

  • Part 1: The 5 Biggest Health Problems of Indoor Cats
  • Part 2: The 5 Biggest Health Problems of Outdoor Cats
  • Part 3: In Defense of Outdoor Cats: Another Vet’s Perspective
Outdoor cats have a greater chance of contact with parasites and infectious diseases. Photo: focusonpc

Part 1: The 5 Biggest Health Problems of Indoor Cats

A typical week full of cat appointments for a veterinarian might look something like this:

  • Leo, 5-year-old DSH [domestic shorthair], vomiting for 2 days
  • Oscar, 7-year-old DSH, check runny eyes
  • Annabelle, 2-year-old Persian, not using the litter box for 1 month
  • BamBam, 5-year-old DSH, scratching himself, just like last year
  • Pumpkin, 4-year-old DLH [domestic longhaired], sneeze/cough
  • Juno, 14-year-old DSH, possibly losing weight and drinking more water

These are some of the most common health problems we see with strictly indoor cats.

1. Vomiting

Young. Old. Healthy. Debilitated. Vomiting is not picky when it wants to bother a cat.

Everyone is familiar with that full-body undulation giving way to a projectile spewing of recycled cat food in various stages of digestion.

Cats often seem to pick your dinnertime or when guests arrive to vomit. Then, some of these cats go back to the food bowl and see if there’s more to eat.

While occasional vomiting is normal for many cats, vomiting is a symptom of many feline diseases. The list of causes for vomiting in cats is long.

  • Cats like to eat or chew on stupid stuff, often causing an intestinal blockage. Swallowing foreign objects that lodge in the GI tract is a common cause for vomiting.
  • Cat toys, a needle and thread, 35 pieces of self-adhesive strips from envelopes, chipmunk heads, Christmas decorations — I never know what I’ll find when I cut into that intestine.

When you bring your cat to the vet because they’ve been vomiting for a week to a month and you think there’s a simple answer, there’s not.

In 1 week alone, I saw cats vomiting from inflammatory GI disease, kidney disease, hyperthyroidism, constipation, eating a rodent, eating house plants and a few cases still undiagnosed.

  • Diagnostics for vomiting include radiographs and blood work, advanced imaging, diet trials and possibly GI biopsies, to name a few.
  • Treatment depends on the cause. Although there are palliative medications to perhaps make a vomiting cat feel better, don’t take the Band-Aid approach if your cat continues to vomit. We need to find out why.

Veterinary pearl of wisdom: Although hairballs are considered a cause of vomiting in the cat, a normal cat develops hairballs and passes them without excessive vomiting. A cat vomiting frequently, even if the cat appears healthy, has an underlying condition. Have your cat checked out.

Know which plants are poisonous to cats and keep them out of your home. Photo: tommyhj

2. Lower Urinary Tract Problems

Many cats are affected by lower urinary tract disease, sometimes referred to as cystitis.

If cats are mildly affected, they exhibit occasional straining to urinate in the litter box or they stop using the box.

  • The urine is often blood-tinged (hematuria), and the cat is passing small amounts of urine frequently (stranguria).
  • In the worst case, the cat cannot pass urine (urinary blockage), which is an extreme medical emergency.

This is a multi-factorial disease, meaning diet, dehydration, viral and bacterial infections, genetic predisposition, metabolism, stress and more may play a role.

  • Basic diagnostics include blood work and urinalysis, a urine culture, radiographs and sometimes an ultrasound.
  • Treatment may include dietary changes, pain and anti-spasmodic medications, and antibiotics.
  • A cat with a urinary blockage must be unobstructed and catheterized. Bladder stones may have to be removed surgically.

Veterinary pearl of wisdom: Change to an all-canned or mostly canned diet if your cat has experienced any symptoms of lower urinary tract disease. Offer multiple sources of clean, fresh water. Keeping your cat as hydrated as possible may prevent recurrence of problems.

3. Respiratory Diseases

Cats are frequently plagued by diseases that cause anything from a mild sneeze to respiratory distress. Symptoms include:

  • Runny nose and sneezing
  • Tearing eyes
  • Discharge from the eyes
  • Conjunctivitis
  • Cough
  • Fever
  • Trouble breathing

Upper respiratory disease in cats is often caused by viruses. Bacterial infections can follow. Theses infections can be mild and self-limiting, chronic or sporadic, or serious. Kittens, geriatric and immunocompromised cats are at greater risk of developing serious respiratory infections.

Feline asthma (also known as bronchitis or allergic bronchitis) is another common respiratory disease.

  • Asthmatic cats can cough, wheeze, gag, stretch their necks out as if to gasp, or draw in a breath and/or exhibit true respiratory distress.
  • Cats experiencing a severe asthmatic attack require emergency intervention, medications and an oxygen cage.

Treatment for respiratory disease can include antibiotics, antivirals, steroids, bronchodilators, inhalers, decongestants and eye medications.

Veterinary pearl of wisdom: Never ignore difficult breathing in a cat. Early intervention can truly be life-saving. Your vet will have to differentiate upper airway disease from lower airway disease, rule out a heart condition and treat appropriately.

4. Dermatologic Disease

Cats are prone to allergies that cause itchy skin, particularly flea allergic dermatitis.

  • Indoor cats can get fleas. Most veterinary dermatologists believe flea allergy is behind a great deal of cat scratching until proven otherwise.
  • Cats can also be allergic to inside and outside environmental allergens and be food allergic.

When a cat is itchy, they will over-groom, bite, scratch and give themselves serious skin lesions.

There are many other dermatologic diseases in cats, including parasitic, neoplastic, bacterial, fungal, autoimmune and inflammatory.

Diagnosis starts with a good history from you and a thorough exam of the cat. If fleas are found or suspected, for example, we treat these first. Skin scrapes, fungal culture for ringworm, food elimination diet trials and possible biopsy are all diagnostic tools in getting to the heart of the itch.

Treatment depends on the diagnosis. This can include a change in diet, steroids, non-steroidal drugs, antibiotics and anti-parasitics.

Veterinary pearl of wisdom: If a cat starts scratching and incurring lesions, this itch will not stop until you discover the cause and treat it. Waiting means worse trauma to the skin, a longer recovery time, more medications and bigger vet bills.

Here are more signs to watch out for if you think your cat is ill:

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5. Kidney Failure

Many house cats develop kidney disease and failure, particularly as they age. Kidney disease is more prevalent in cats than in our other pets.

  • The most common cause of kidney disease and failure in cats is age.
  • But not every older cat has kidney disease, and younger cats can be affected, too.
  • Exposure to toxins that damage the kidneys, as well as infections, dehydration, poor diet and stress on the body caused by other illnesses can all affect the kidneys.
  • Congenital kidney disease and cancer also occur.

Advances in veterinary care, particularly how we care for our aging population of cats, have made kidney disease much more rewarding to treat. Diagnosis is largely through blood work. A full work-up includes X-rays and/or ultrasound, culture of the urine, and blood pressure monitoring.

Modifications in diet, multiple medications and additional sources of hydration help a cat who is in kidney failure.

Veterinary pearl of wisdom: Don’t ignore subtle weight loss, mild lack of appetite or increased thirst in your cat. Kidney disease can behave like a cat burglar, sneaking up on your pet, so don’t disregard the early warning signs.

Parasites that your outdoor cat brings into the house may put you at risk. Photo: Jorge Gonzalez

Part 2: The 5 Biggest Health Problems of Outdoor Cats

Part 1 of this article focused on the common maladies of indoor cats. Now outdoor cats get their turn.

The outdoor cats I see come in 2 varieties:

  • There are the indoor/outdoor cats who get veterinary care and have a good home but are allowed to go outside.
  • And then there are the good ol’ barn cats — the strays who pretty much fend for themselves.

Here are the top 5 health problems of outdoor cats that this veterinarian sees:

1. Parasites

Cats who live outdoors share their bodies with lots of other little creatures: parasites.

  • Endoparasites live inside the body, invading the GI tract, the lungs and the heart.
  • Ectoparasites live on the outer body, invading the skin and the ears.

When a cat has GI parasites (roundworms, hookworms, tapeworms), their symptoms usually include vomiting and/or diarrhea, weight loss and anorexia. Some of these parasites can also create a cough because they migrate through the lungs.

Identified by a fecal test, these buggers are treated with drugs called anthelmintics.

  • Unfortunately, many outdoor cats don’t get the benefit of being “wormed,” and they live their lives with parasites.
  • Although adult cats can live with a certain burden of parasites, a heavy worm burden in young kittens or immunocompromised cats can be life-threatening.
  • Parasites such as lungworm and heartworm are also common in outdoor cats, more so in some areas of the country than others.
  • Many of these cats suffer from a cough, but the damage done to the lungs can be life-threatening in some cats.

Lungworms can be treated with the proper anthelmintic medication.

Heartworm is not easily treated in the cat, but the cough and lung damage it causes can be helped with medications. These cats usually present as having “asthma.”

An outside enclosure could be a great compromise for those who want their cat to experience the outdoors safely. Photo: Mimzy

2. Fleas and Other Ectoparasites

  • Outdoor cats can have fleas — even in Alaska.
  • They can also have ear mites, lice, ticks and, less commonly, maggots or cuterebra.
  • Some cats tolerate fleas and the like, and learn to live with them. Others are super sensitive, scratching themselves, giving themselves swollen ears and living very uncomfortable lives.
  • It goes without saying that some of these parasites are a risk to you and your home environment as well.

Once identified, all of these ectoparasites can be treated, but the cat may need other supportive treatment as well.

Medications to stop the itch and treat the skin or ear infections take time and a dedicated human. That good ol’ barn cat needs some TLC to get better.

Fleas are also the biggest source of tapeworms and can transmit blood parasites.

  • If your cat goes outside, I believe in treating fleas proactively every month.
  • House cats can get fleas from other animals who go out, from hunting rodents in the house, or by spending time near outdoor areas.
  • Talk with your veterinarian about risk and prevention.
Outdoor cats may contract FeLV and FIV during fights with other outdoor cats who are infected. Photo: hkase

3. Retroviruses: FeLV and FIV

Other infected cats can transmit serious viruses to your outdoor cat: feline immunodeficiency virus (FIV) and feline leukemia (FeLV).

  • Kittens can contract these viruses from their mother.
  • Adult cats contract the viruses from another cat either by friendly grooming, unfriendly contact (such as cat bites and fights), sharing dishes and food, and any other contact with bodily fluids.

Cat bites are a big cause of FIV transmission. Tomcats who fight can inflict deep puncture wounds, and the saliva from the infected cat transmits the virus to an opponent.

  • Vaccinating your cat against FeLV is helpful but not 100% protective.
  • The FIV vaccine is much more controversial.

Cats can live with these viruses for several years before becoming sick.

  • FeLV is a more serious disease and usually causes severe anemia, tumors (lymphoma) and other syndromes associated with immunosuppression.
  • FIV cats may live long lives without symptoms, but the virus can also create an acquired immunodeficiency syndrome with associated health problems.

Keeping your cat away from infected cats is the best way to prevent transmission of retroviruses, but this is virtually impossible if your cat goes outside.

4. Trauma

An outside cat is at great risk for trauma.

These cats face wild predators, other cats and vehicles. They get caught in fences, locked up in garages or outbuildings, fall from high places — the list goes on.

Lots of people talk themselves into a false sense of security by thinking their indoor/outdoor cat “just stays by the house.” But at some point, most of these sensible or street-savvy kitties get into some kind of trouble.

If you let your cat outdoors, you must be willing to accept the consequences — all outdoor cats are at risk for trauma.

Do you know where your outdoor cat goes? Check out this video:

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5. Vomiting

Just like indoor cats, outdoor cats can also suffer from diseases and syndromes that cause vomiting — not to mention the fact that they are at risk for eating many disgusting or toxic things.

An outdoor cat who comes to the veterinarian and is sick or vomiting is a true challenge because the possible causes are many. And if this outdoor cat hasn’t been to the vet recently (or ever), we have to start from scratch.

  • Has the cat lost weight? How much and in what time?
  • What is the FeLV/FIV status of this cat? Even if previously tested negative, they could have contracted one of these viruses recently from a warring enemy.
  • What does the cat eat? Assume anything.
  • How long has this cat been sick? Since last winter? Depending on how little the human sees this outdoor cat, this question often can’t be answered.

Unfortunately, outdoor cats are often on the budget health plan. A “stray” cat might be brought in by a good Samaritan who has fed him through the winter, but “he’s not really my cat.”

So say the cat is brought in — flea-infested, coughing and sneezing; an old wound on his paw; thin and not eating the food on offer this week.

An estimate for an FeLV/FIV test, other blood work, X-rays, wound treatment and other supportive care as indicated can shock good Samaritan. Add to this the cost of flea medication, ear mite treatment and worming. Did I mention he’s not neutered and is now under a rabies quarantine?

Oh, boy — this cat might not live to see next season.

This might be time for one of my vet techs or myself to adopt him or get help from our regional shelter or the state program. No wonder most of us in the veterinary world have at least 5 cats.

When at all possible, keep your cat close to you in their own kingdom.

Below, in Part 3 of this article on indoor cats vs. indoor cats, a different veterinarian weighs in — and this vet feels pretty strongly that cats deserve time outside.

Families where I live generally let their cats roam the great outdoors — allowing them to be cats. Photo: t_abdelmoumen

Part 3: In Defense of Outdoor Cats: Another Vet’s Perspective

This section of the article was written by Dr. Pippa Elliott, BVMS, MRCVS.

Does your cat roam free outside? If not, why not?

I live in the United Kingdom, where 90% of our cats go outside unsupervised, meaning only 10% are exclusively indoor pets.

Contrast this with the United States, where organizations such as the ASPCA actively promote keeping cats indoors.

I’m aware that “indoor cats vs. outdoor cats” is a sensitive topic with entrenched opinions on both sides of the Atlantic.

My aim below is to explain why the “outdoor” option isn’t as bonkers or irresponsible as it might appear. Maybe we can open up a discussion about why it’s important to provide mental stimulation for our cats.

Lack of Predators

Straight out, let’s get one issue out of the way: Here in the U.K., we don’t have coyotes, raccoons or alligators that want to eat our pets.

We do have urban foxes, but cats keep out of their way (and foxes have easier pickings in trash bins).

So predators aren’t a concern here as in the United States — unless, of course, you count the car.

  • Unfortunately, around 25% of U.K. cats under 1 year old are involved in traffic accidents.
  • However, the simple act of allowing the cat out during the day (and keeping them in at night) vastly reduces this risk, because most such car accidents happen at night.

OK, so I gave you a pretty scary statistic there, which arguably makes an open-and-shut case for keeping your cat indoors.

So why is it that 90% of U.K. cats go outside unsupervised?

Oh, and if you’re wondering, our “outdoor cats” are family members. They are valued pets who are at liberty to sleep on a sofa or go outside whenever they want via a cat flap — they’re not strays or feral cats.

Cats Will Be Cats

The answer lies in the U.K. attitude of simply allowing cats to be cats.

By giving cats free access to the outdoors, they are able to express natural behaviors. They can climb, claw, pounce, swipe, pad or gallop as the mood takes them.

In short, they exercise both their mind and body as nature intended.

Cats are hunters with a psyche geared toward scenting and ambushing — even if it’s only in play. And when they’re not hunting, they are washing their coat to keep it odor-free, and only then does the cat sleep.

Don’t get me wrong — I’m not saying we starve our cats or that they are all avid hunters. Far from it. We provide food, but our cats go outside to mimic hunting behavior. They:

  • Follow scents and suss out who has passed through their patch
  • Patrol the flower borders
  • Sunbathe
  • Chew grass
  • Sharpen their claws on bark
  • Climb a tree
  • Chase off intruders
  • Urinate/defecate on soil
  • And perhaps stroll around to the neighbors to see if they can get a treat

In short, these indoor/outdoor cats entertain themselves by doing catlike things.

On average, outdoor cats have a life expectancy into their high teens, similar to that of indoor cats. Photo: marcus_t_ward

Indoor Risks

Indoor cats get bowls of food. They eat, wash and are then left feeling bored and listless — unless you provide mental stimulation and entertainment.

Boredom may cause indoor cats to overeat and face an increased risk of diabetes.

Cats with access to outdoors, on the other hand, tend to be fitter, slimmer and less likely to have behavioral issues, such as inappropriate territory marking indoors.

On the minus side, yes, there is a greater chance of contact with parasites and infectious diseases. But we can control these with regular deworming, flea treatments and vaccination.

Do Indoor Cats Really Live Longer Than Outdoor Cats?

One of the facts often quoted in favor of indoor cats is they live longer than outdoor cats.

But this argument is flawed because once young cats who die in traffic accidents are taken out of the equation, the statistics level out.

Indeed, outdoor cats who live beyond 1 year have a life expectancy into the high teens — just like indoor cats.

And if you thought being an indoor cat removes all risk, think again:

  • They are more exposed to harmful substances, such as tobacco smoke and household chemicals.
  • Most important, indoor cats are more likely to express their frustration in behavioral problems, such as clawing, fighting or inappropriate urination, which could lead to them being rehomed or euthanized.

Do you think the kitties in this video are debating indoor cats vs. outdoor cats?

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Indoor Cats vs. Outdoor Cats: It’s a Personal Choice

Whether you have an indoor or outdoor cat is very much a personal choice, and I’m not seeking to change your mind, especially if you feel strongly.

All I’m suggesting is the options aren’t always as clear-cut as popular culture would have you believe — and what we should always do is put cat welfare first.


This article on indoor cats vs. outdoor cats was written by a veterinarian, Dr. Debora Lichtenberg, VMD, with contributions from Dr. Pippa Elliott, BVMS, MRCVS and cat behaviors writer T.J. Banks. It was last reviewed and updated Dec. 21, 2018.