That old saying "laughter is the best medicine" has more than a little truth in it. When laughter bursts forth, your metabolism picks up, muscles are massaged, and neurochemicals stream into the blood. You feel relaxed — and you raise your guard against depression, heart disease, and pain.
Now researchers think laughter’s salutary role includes boosting the immune system. New studies indicated that laughter can increase concentrations of salivary immunoglobulin A (IgA) — an antibody linked to lower rates of upper respiratory illnesses. In fact, it's been found that IgA levels are naturally high in people who regularly battle adversity with humor. In addition, laughter decreases cortisol, an immune suppressor, which has a tremendous influence on the immune system. This decrease allows interleukin-2 and other immune boosters to express themselves.