If you have pets you already know the joy and love they bring to your life. Now science is confirming just how good they really are for you — both mentally and physically.

How do they help? One theory is that pets boost our oxytocin levels. Also known as the "bonding hormone" or "cuddle chemical," oxytocin enhances social skills, decreases blood pressure and heart rate, boosts immune function and raises tolerance for pain. It also lowers stress, anger and depression.

No surprise then that keeping regular company with a dog or cat (or another beloved beast) appears to offer all these same benefits and more. Read on to discover the many impressive ways a pet can make you healthier, happier and more resilient.

1. Pets alleviate allergies and boost immune function

One of your immune system's jobs is to identify potentially harmful substances and unleash antibodies to ward off the threat. But sometimes it overreacts and misidentifies harmless stuff as dangerous, causing an allergic reaction. Think red eyes, itchy skin, runny nose and wheezing. You'd think that having pets might trigger allergies by kicking up sneeze-and-wheeze-inducing dander and fur. But it turns out that living with a dog or cat during the first year of life not only cuts your chances of having pet allergies in childhood and later on but also revs up your immune system and lowers your risk of eczema and asthma. In fact, just a brief pet encounter can invigorate your disease-defense system. In one study, petting a dog for only 18 minutes raised immunoglobulin A (IgA) levels in college students' saliva, a sign of robust immune function.

2. Pets up your fitness quotient

This one applies more to dog owners. If you like walking with your favorite canine, chances are you're fitter and trimmer than your non-dog-walking counterparts and come closer to meeting recommended physical activity levels. One study of more than 2,000 adults found that regular dog walkers got more exercise and were less likely to be obese than those who didn't walk a dog. In another study, older dog walkers (ages 71-82) walked faster and longer than non-pooch-walkers, plus they were more mobile at home.

A small dog runs alongside its human companionDog owners who take their canine companions on walks tend to be trimmer and fitter than their fellow dog-less peers. (Photo: AMatveev/Shutterstock)

3. Pets dial down stress

When stress comes your way, your body goes into fight-or-flight mode, releasing hormones like cortisol to crank out more energy-boosting blood sugar and epinephrine to get your heart and blood pumping. All well and good for our ancestors who needed quick bursts of speed to dodge predatory saber-toothed tigers and stampeding mastodons. But when we live in a constant state of fight-or-flight from ongoing stress at work and the frenetic pace of modern life, these physical changes take their toll on our bodies, including raising our risk of heart disease and other dangerous conditions. Contact with pets seem to counteract this stress response by lowering stress hormones and heart rate. They also lower anxiety and fear levels (psychological responses to stress) and elevate feelings of calmness.

4. Pets boost heart health

Pets shower us with love so it's not surprising they have a big impact on our love organ: the heart. Turns out time spent with a cherished critter is linked to better cardiovascular health, possibly due to the stress-busting effect mentioned above. Studies show that dog owners have a lower risk of heart disease, including lower blood pressure and cholesterol. Dogs also benefit patients who already have cardiovascular disease. They're not only four time more likely to be alive after a year if they own a dog, but they're also more likely to survive a heart attack. And don't worry, cat owners — feline affection confers a similar effect. One 10-year study found that current and former cat owners were 40 percent less likely to suffer a heart attack and 30 percent less likely to die of other cardiovascular diseases.

5. Make you a social — and date — magnet

Four-legged companions (particularly the canine variety that pull us out of the house for daily walks) help us make more friends and appear more approachable, trustworthy and date-worthy. In one study, people in wheelchairs who had a dog received more smiles and had more conversations with passersby than those without a dog. In another study, college students who were asked to watch videos of two psychotherapists (depicted once with a dog and once without) said they felt more positively toward them when they had a dog and more likely to disclose personal information. And good news for guys: research shows that women are more willing to give out their number to men with a canine buddy.

A woman and a man in a park with a labradorA dog can make you appear friendlier and more approachable to others. (Photo: CandyBox Images/Shutterstock)

6. Provides a social salve for Alzheimer's patients

Just as non-human pals strengthen our social skills and connection, cats and dogs also offer furry, friendly comfort and social bonding to people suffering from Alzheimer's and other forms of brain-destroying dementia. Several canine caregiver programs now exist to assist at-home dementia patients with day-to-day tasks, such as fetching medication, reminding them to eat and guiding them home if they've wandered off course. Many assisted-living facilities also keep resident pets or offer therapy animal visits to support and stimulate patients. Studies show creature companions can reduce behavioral issues among dementia patients by boosting their moods and raising their nutritional intake.

7. Enhances social skills in kids with autism

One in nearly 70 American kids has autism (also known as autism spectrum disorder, or ASD), a developmental disability that makes it tough to communicate and interact socially. Not surprisingly, animals can also help these kids connect better to others. One study found that youngsters with ASD talked and laughed more, whined and cried less and were more social with peers when guinea pigs were present. A multitude of ASD animal-assisted therapy programs have sprung up in recent years, featuring everything from dogs and dolphins to alpacas, horses and even chickens.

Animals help kids with autism learn social skillsAnimal-assisted therapy helps kids with autism and other developmental disabilities learn social skills. (Photo: UCI UC Irvine/flickr)

8. Dampens depression and boosts mood

Pets keep loneliness and isolation at bay and make us smile. In other words, their creature camaraderie and ability to keep us engaged in daily life (via endearing demands for food, attention and walks) are good recipes for warding off the blues. Research is ongoing, but animal-assisted therapy is proving particularly potent in deterring depression and other mood disorders. Studies show that everyone from older men in a veterans hospital who were exposed to an aviary filled with songbirds to depressed college students who spent time with dogs reported feeling more positive.

9. Defeats PTSD

People haunted by trauma like combat, assault and natural disasters are particularly vulnerable to a mental health condition called post-traumatic stress disorder (PTSD). Sure enough, studies show that the unconditional love — and oxytocin boost — of a pet can help remedy the flashbacks, emotional numbness and angry outbursts linked to PTSD. Even better, there are now several programs that pair specially trained service dogs and cats with veterans suffering from PTSD.

10. Fights cancer

Animal-assisted therapy helps cancer patients heal emotionally and physically. Preliminary findings of a clinical trial by the American Humane Association shows that therapy dogs not only erase loneliness, depression and stress in kids fighting cancer, but canines can also motivate them to eat and follow treatment recommendations better — in other words participate more actively in their own healing. Likewise, new research reveals a similar lift in emotional well-being for adults undergoing the physical rigors of cancer treatment. Even more astounding, dogs (with their stellar smelling skills) are now being trained to literally sniff out cancer.

11. Puts the kibosh on pain

Millions live with chronic pain, but animals can soothe some of it away. In one study, 34 percent of patients with the pain disorder fibromyalgia reported pain relief (and a better mood and less fatigue) after visiting for 10-15 minutes with a therapy dog compared to only 4 percent of patients who just sat in a waiting room. In another study, those who had undergone total joint replacement surgery needed 28 percent less pain medication after daily visits from a therapy dog than those who got no canine contact.