Cats sometimes behave in puzzling ways — like running outside to chow down on grass and promptly throwing up. Or maybe they love to roll around with your shoes, or chill in their litter box instead of on the fancy cat furniture you got them. 

Of course, cats are curious, intelligent creatures, with individual personalities that make them unique. So, you might not always know for certain which odd behaviors fall into the category of "cat quirks" and which might suggest a health issue or other cause for concern. 

Most of the time, you don't have any reason to worry, since your feline pal is probably just doing cat things. When it comes to eating grass, for instance, experts have yet to link this behavior to any health issue. 

Read on to learn more about six common — but potentially confusing — cat behaviors and when you'll want to reach out to a veterinarian. 

Important: If your cat seems very distressed, suddenly begins to spend most of the day hiding, or has lingering signs of illness, you'll want to call a vet right away. 

There's no one accepted theory as to why cats like to eat grass, says Dr. Georgina Ushi, a veterinarian at Fuzzy, an online platform that connects pet parents remotely with vets. Research remains limited, but current theories suggest: 

If you're concerned about digestive issues or signs of a potential nutrient deficiency, like lethargy, appetite loss, or weight loss, your vet can offer more guidance and recommend tests for your pet. 

Latest research: A 2021 study asked cat owners why they believed their cats ate plants. One of the most common theories? Cats eat grass to expel hairballs or induce vomiting. But the researchers found that less than 50% of the cats included in the study vomited after eating plants, so this may not be a key motivation for grass eating.

In short, cats eating grass is a fairly common behavior and probably not a big deal — unless they're munching on treated grass. 

If you treat your lawn with chemicals to kill weeds or insects, you'll want to keep your cat inside and off the grass. Eating treated grass — or walking on treated grass and then licking and grooming their paws — can make your cat very sick and may even be fatal. 

A few chemicals commonly in lawn care that pose a risk to cats include: 

Important: If your cat may have eaten grass treated with pesticides or herbicides and they have vomiting or diarrhea, mouth lesions, increased salivation, or seem lethargic, head to a vet right away. These signs can suggest poisoning, Ushi says. 

A cat grass kit offers a safe alternative to chemically-treated lawns. These kits, which contain edible grasses like rye, wheat, or oat grass, make a great indoor option for cats that love nibbling on grass, according to Ushi. You can buy these kits online or in your local pet shop. 

Achoo! Yes, cats sneeze just like humans do — and often for many of the same reasons, Ushi says, such as:

While sneezing due to airborne irritants doesn't typically require intervention, other causes of sneezing, such as infection, may require treatment from a vet. 

Ushi says your vet may recommend the following medications for chronic respiratory conditions, depending on whether the cause is bacterial or viral:

All cats groom and scratch themselves to some degree. But overgrooming or excessive scratching can suggest an underlying medical issue or stress, says Molly DeVoss, certified feline training and behavior specialist. 

Signs of overgrooming may include:

DeVoss says scratching due to allergies typically ebbs and flows with exposure to allergens and the change of seasons. 

Other medical reasons for excessive scratching or grooming include: 

Cats might also overgroom due to anxiety, boredom, or obsessive-compulsive disorder (OCD), Ushi says. If your cat's overgrooming relates to stress, they'll likely have other behavioral symptoms. For instance, they might: 

Treatment for overgrooming involves addressing the underlying issue. For example, a cat with allergies that cause itchy skin may benefit from taking antihistamines. 

For behavioral overgrooming, DeVoss says identifying the trigger is crucial. Many cats have trouble with natural cat behaviors — grooming excessively or not at all, for instance — due to stress, DeVoss says. 

As a start, it may help to consider any changes in your cat's environment or daily life. For example, maybe you've recently spent more time away from home, changed their feeding time, or donated their favorite piece of furniture. 

Quick tip: DeVoss recommends contacting a feline behavior specialist if you're struggling to identify your cat's stress or anxiety triggers. In some cases, overgrooming can suggest poor overall well-being, due to things like a lack of nutrition, boring environment, or underlying health concerns. 

Sometimes, a lack of appetite can mean your cat is sick — but cats may also ignore their food because: 

Quick tip: If you've recently introduced a puzzle feeder and your cat suddenly seems uninterested in its food, it may be worth swapping back to its regular bowl or container to check if they start eating again. As one 2021 study suggests, many cats don't like working for their meals.

Your cat sitting in their litter box may seem a little gross, but it's probably not a reason to worry. 

"Cats love to be in small cozy places. Some litter boxes provide that space for them, so they can rest, hide, and take a short break from play," Ushi says.

Additionally, DeVoss says cats gravitate toward familiar scents and that shelter cats often show a preference for a litter box filled with familiar smells. 

"In a home environment, a cat hiding or lying in the litter box could indicate a medical issue, feelings of stress, or territorial insecurity," she says. 

If your cat is sitting in a litter box for lengthy periods — over 12 hours at a time, for instance — something might be wrong, Ushi says. 

If you don't want your cat to hang out in their literal bathroom all day, you might try creating new, appealing hiding spots around your home. Aiming for variety can give your cat options. 

For instance, you might try a mix of: 

Important: Ushi recommends heading to the vet if this behavior persists — particularly if your cat doesn't eat for 24 hours, seems to have no energy, or shows persistent changes in their usual behavior, like avoiding you if they typically come running when you call. 

One of the most common reasons cats do their business outside the litter box is a urinary issue. These include urinary cystitis, or an inflammation of the bladder wall, and urinary tract infections (UTIs). 

Signs your cat may have a urinary issue include:

Other potential medical reasons for this behavior include:

Addressing underlying medical issues with the help of a veterinarian may prevent defecation and urination outside the litter box. 

Reasons for soiling outside the litter box aren't always medical, though. A cat may avoid the litter box because:

Identifying non-medical reasons for skipping the litter box can take some time and experimentation. As a start, you might try changing the box, moving it, or opting for a different litter material to see how your cat responds. 

If your cat has a habit of marking its territory, your vet may recommend anti-anxiety drugs in addition to environmental changes. But medications don't offer a permanent solution, and they may not work for all cats.

Any major changes in your cat's behavior may suggest an underlying health concern. If you notice any of the following red flags, you'll want to make an appointment with your vet right away: 

Weird behaviors like eating grass and ignoring food can be signs of underlying health issues, but your cat may also just be acting like a cat. 

Knowing their usual quirks can make it easier to spot signs of potential health problems. Keeping track of how much they usually eat and drink, for instance, can make it easier to recognize when they suddenly want more or less than usual. 

You can help your cat live a full, healthy life by making sure to keep tabs on their routine and habits, Ushi says. And it's always a good idea to schedule yearly vet visits and provide plenty of enrichment in the form of activities and toys. 

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