General:  Decreased level of distress if any, more alert after, feeling of euphoria. 

Head, Eyes, Ears, Nose and Throat:  Increased Oxygenation, tears provide natural secretions to clean and lubricate, relaxed muscles in head and face, great workout for facial muscles to decrease sagging, pleasant sound of others laughing around you. 

Neck:  Decrease neck tension with muscle relaxation, increased blood flow through caroids and thyroid. 

Cardiovascular (Heart):  Increased oxygenation, laughing is aerobic like an “internal jogging,” transient increase in heart rate, resting blood pressure may decrease, relaxed blood vessels, increased blood flow, good heart “workout”. 

Pulmonary (Lungs):  Increased respiration and empties lungs of more air than it takes in resulting in a cleaning effect – similar to deep breathing, increased blood flow through lungs, diaphragm workout with increased air flow, good chest physiotherapy to loosen secretions (especially when your friend slaps your back). 

Gastrointestinal (Digestive):  Abdominal organs massage with belly laugh, enhanced digestive enzyme secretion.

Genitourinary (Kidneys and Bladder):  Increased blood flow leads to increased filtering by kidneys.  If you laugh too hard, you may pee in your pants! 

Hematologic (Blood and Lymph Glands):  Circulating red blood cells to oxygenate, enhanced white blood cell activity (linked to immunologic) below.

Immunologic (Immune System):  Activates the immune system – i.e. increased natural killer cells, activated T lymphocytes, immunoglobulin A and G, gamma interferon, and complement C3. 

Endocrine (Hormones):  Decreases  “stress” hormones such as cortisol and epinephrine.  Dopamine and growth hormone levels decreased (involved in “fight or flight reactions”)

Rheumatologic (Joints): Increased pain tolerance, distraction from pain such as aches, arthritis. 

Musculoskeletal:  Muscle relaxation, diaphragm and abdominal workout, increased blood flow to muscles. 

Neuropsychiatric:  Positive emotions that can enhance conventional treatments can reduce pain and aid in the overall healing process.  Laughter provides an opportunity for the release of uncomfortable emotions which if held inside, may create biochemical changes that harmful to the body.  Ability to sense and appreciate humor can buffer the mood disturbances which occur in response to negative life events.