Humor changes our biochemical state. Laughter decreases stress hormonesand increases infection-fighting antibodies. It increases our attentiveness, heart rate, and pulse.Humor improves brain function and relieves stress.Laughter stimulates both sides of the brain to enhance learning. It eases muscle tension and psychological stress, which keeps the brain alert and allows people to retain more information.Humor help muscle relaxation.Research has shown that muscle relaxation results from a good belly laugh.

One study even showed that people using a biofeedback apparatus were able to relax muscles more quickly after watching funny cartoons than after looking at beautiful scenery. You can see this effect in your own laughter, if you look for it. In my keynote addresses, I have a routine in which I get everyone in the room doing belly laughter for half a minute.

Afterwards, I ask them what changes they notice in their bodies. The first comment is usually, “I feel a lot more relaxed.” The next time you have a good long laugh, look for this feeling of relaxation and reduced tension.

Laughter lowers blood pressure.
People who laugh heartily on a regular basis have lower standing blood pressure than the average person. When people have a good laugh, initially the blood pressure increases, but then it decreases to levels below normal. Breathing then becomes deeper which sends oxygen enriched blood and nutrients throughout the body.
Humor contribute to pain reduction Many patients discover this in their own experience. Rheumatoid arthritis patients who report more chronic pain, for example, also say they look for humor more often in everyday life. They have learned that humor helps manage their pain. Consistent with this idea, one study showed that when elderly residents of a long-term care facility watched funny movies, the level of pain they experienced was reduced. In a study of 35 patients in a rehabilitation hospital, 74% agreed with the statement, “Sometimes laughing works as well as a pain pill.” The patients had such conditions as traumatic brain injury, spinal cord injury, arthritis, limb amputations, and a range of other neurological or musculoskeletal disorders.

Laughter protects the heart.
Laughter, along with an active sense of humor, may help protect you against a heart attack, according to the study at the University of Maryland Medical Center (cited above). The study, which is the first to indicate that laughter may help prevent heart disease, found that people with heart disease were 40 percent less likely to laugh in a variety of situations compared to people of the same age without heart disease.
Humor helps us stay emotionally healthy
A healthy sense of humor is related to being able to laugh at oneself and one’s life. Laughing at oneself can be a way of accepting and respecting oneself. Lack of a sense of humor is directly related to lower self esteem. (Note that laughing at oneself can also be unhealthy if one laughs as a way of self-degradation.)
Humor is good for the digestive system.
Perhaps it’s best to play out the reversal of that. Think about how your stomach and intestines react when you are stressed, nervous or angry.
Humor reduces anger and anxiety.
You feel empowered , more in control of your emotions, it “lightens” the environment around you and increases productivity. Helpful in the workplace and at home.
Laughter and humor are social characters.
They liked to be shared and are wonderfully addictive and contagious.