To understand the connection between laughter and the lymphatic and immune systems, it is first important to understand what the lymphatic system is all about.

The lymphatic system is the cleansing agent of the human body

lymphatic systemThe lymphatic system is a highly efficient cleaning conglomerate that is the backbone of the immune system. It is an extensive, mesh-like network of very fine vessels (intertwined with the venous system yet separate from blood vessels) located immediately beneath the skin and above the muscles. It continuously collects waste materials from all over the body (dead blood cells, pathogens, toxins, etc.) that are deposited into the tissues via blood capillaries. It then cleans that fluid and returns it back into the circulating blood at the neck. It also removes excess fluid and waste products from the interstitial spaces between the cells, and more.

The lymphatic system has a number of small swellings called lymph nodes. These are clusters of “cleaning stations” interspersed along the lymphatic pathways, primarily in the armpit, neck, chest, abdomen and groin. They specialize in producing white blood cells (lymphocytes) to clean the fluid, antibodies to defend against future predators, and macrophages to remove all manner of unwanted debris.

The link between laughter and the lymphatic system

What does laughter have to do with the lymphatic system? The answer is so simple it is easy to miss:

Unlike the circulatory system which has the heart to pump the blood in a continuous circle to all parts of the body, the lymphatic system is a simple transport system with no pump. Lymphatic fluid moves by inertia in a semi-circular manner, always moving fluid toward the heart.

Despite having no pump to move it however, the lymphatic system is capable of being manually moved.

Biophysical studies have shown that belly laughter accomplishes the diaphragmatic breathing necessary (diaphragm fluttering up and down at a very quick rate) to create a strong negative pressure within the thoracic duct (the largest lymphatic vessel in the body). Under negative pressure, the lymphatic fluid seeks an area of lesser pressure, thus shooting the lymph up and out through lymphatic vessels, increasing the speed and flow up to 10-15 times its normal rate of flow.

The increased flow of lymphatic fluid means more lymph is passing through lymph nodes, which itself means that more lymphocytes (t and b-cell lymphocytes, plus NK cells – the natural killer cells) are produced. Increased number of lymphocytes circulating in the blood means better immunity toward ALL diseases, especially cancer.

Any muscular movement will stimulate and increase the flow of lymphatic fluid, but laughter might prove to be one of the most painless and beneficial for accomplishing that goal.

In clear: when you laugh, the diaphragm becomes a powerful pump for your lymphatic circulation, much like your heart serves as the central pump that propels blood through your blood vessels. This assists the lymphatic vessels in carrying this fluid through your body and helps your lymph nodes to clean and filter this fluid, removing waste products, dead cells, and even unwanted microorganisms. Maintaining clean body fluids is important because these are necessary for you to be at your best. Increased lymphatic flow = an elevated, improved immune system just by the simple nature of more lymph flowing through the nodes, thus producing more lymphocytes, antibodies, etc.

More good news

Engaging the diaphragm with ANY type of deep breathing (laughter included), immediately engages the parasympathetic nervous system. The parasympathetic nervous system signals ALL body systems to SLOW down, thus producing “feel good” hormones (endorphins) that signal stress hormones to cool it. Once that signal is received, blood pressure drops, heart rate slows and an overall glow of “happiness in the moment” replaces anxiety/stress – the perfect “domino effect”.

Watching a one-hour comedy video for example has been found to produce:

  • Increased number and activation of T cells;
  • Increased number of Helper T cells (the cells attacked by the AIDS virus);
  • Increased ratio of Helper/Suppressor T cells;
  • Increased number and activity of Natural Killer (NK) cells;
  • Increased levels of Gamma Interferon;
  • Increased number of B cells.

Here are some quotes from famous doctors:

  • The simple truth is that happy people generally don’t get sick.” – Bernie Siegel, M.D. (an internationally recognized expert in the field of cancer treatment and complementary holistic medicine)
  • The best clinicians understand that there is an intrinsic physiological intervention brought about by positive emotions such as mirthful laughter, optimism and hope.” – Lee Berk, DrPH, Assoc Res Pro Loma Linda School of Medicine
  • “For the most part, when you go and get medical treatment, a clinician is not necessarily going to tell you to take two aspirins and watch Laurel and Hardy, but the reality is that’s where we are and it’s more real than ever. There’s a real science to this. And it’s as real as taking a drug.” – Lee Berk, DrPH, Assoc Res Pro Loma Linda School of Medicine
  • Daily opportunities for laughter are important for patients with diabetes” – Keiko Hayashi, RN, PhD
  • Believe it or not, having a really hearty chuckle can help too. This is because laughing gets the diaphragm moving and this plays a vital part in moving blood around the body.” – Dr. Andrea Nelson, University of Leeds School of Healthcare

The claim: Laughter strengthens immunity

The fact (measured): Yes, it does


Laughter raises DHEA (dehydroepiandrosterone) levels (a steroid hormone produced by the adrenal glands). Many researchers consider high levels of DHEA a marker of health in the body (for the record studies indicate that DHEA, which declines with age, also has anti-aging, anti-cancer, and anti-obesity effects and can enhance mental abilities.)

A small study showed that laughter significantly reduces levels of inflammation-triggering cytokines in people with rheumatoid arthritis. This may partly explain the miraculous recovery of Norman Cousins (he reported that as little as five minutes of hearty laughter would cause a 53 percent increase in the disease-fighting ability of his blood.)

Other research suggests that after viewing humorous films, people with asthma become more resistant to flareups, those with allergies suffer fewer symptoms, and children with allergic skin rashes sleep more easily.

Relevant studies

Exposure to a humorous stimulus increased NK cell activity; increased SIgA; increased serum IgA, IgG, IgM:

  • Bennett MP, Zeller JM, Rosenberg L, McCann J. The effect of mirthful laughter on stress and natural killer cell activity. Altern Ther Health Med. 2003;9 (2):38-45.
  • Takahashi K,Iwase M, Yamashita K, et al. The elevation of natural killer cell activity induced by laughter in a crossover-designed study. Int J Molecular Med. 2001;8)6);645-650.
  • McClelland R, Cheriff A. The immunoenhancing effects of humour on secretory IgA and resistance to respiratory infections. Psychol Health.1997;12 (3):329-344.
  • Lefcourt H, Davidson-Katz K, Kueneman K. Humor and immune system functioning. Humor: Int J Humor Res. 1990;3:305-321.
  • Dillon KM, Minchoff B, Baker KH. Positive emotional status and enhancement of the immune system. Int J Psychiatry Med. 1985-1986;15 (1):13-18.
  • Labott SM, Ahleman S, Wolever ME, Martin RB. The physiological and psychological effects of the expression and inhibition of emotion. Behav Med. 1990;16 (4):182-189.
  • Martin RA, DobbinJP. Sense of humor, hassles, and immunoglobulin A: evidence for a stress-moderating effect of humor. Int J Psychiatry Med. 1988;18 (2):93-105.
  • Kimata H. Reduction of plasma levels of neurotrophins by laughter in patients with atopic dermatitis. Pediatr Asthma Allergy Immunol. 2004;17 (2):131-135.

Mirthful laughter decreased serum pro-inflammatory cytokine and increased anti-inflammatory cytokine levels, growth hormone, and IGF-1; reduced serum interleukin-6 levels:

  • Matsuzaki T, Nakajima A, Ishigami S, Tanno M, Yoshino S. Mirthful laughter differentially affects serum pro- and anti-inflammatory cytokine levels depending on the level of disease activity in patients with rheumatoid arthritis. Rheumatology (Oxford). 2006;45 (2):182-186.
  • Ishigami S, Nakajima A, Tanno M. Matsuzaki T, Suzuki H, Yoshino S. Effects of mirthful laughter on growth hormone, IGF-1 and substance P in patients with rheumatoid arthritis. Clin Exp Rheumatol. 2005;23 (5):651-657.
  • Yoshino S, Fujimori J, Kohda M. Effects of mirthful laughter on neuroendocrine and immune systems in patients with rheumatoid arthritis. J Rheumatol. 1996;23 (4);793-794.
  • Nakajima A, Hirai H, Yoshino S. Reassessment of mirthful laughter in rheumatoid arthritis. J Rheumatol 199;26 (2):512-513.

Laughter and humor reduced allergen-induced wheat reactions, reduced allergen-specific IgE production, and improved night-time wakening:

  • Kimata H. Effect of humor on allergen-induced wheat reactions. JAMA. 2001;285 (6),738.
  • Kimata H. Reduction of allergen-specific IgE production by laughter. Eur J Clin Invest. 2004;34 (9):76-77.
  • Kimata H. Viewing humorous film improves nighttime wakening in children with atopic dermatitis. Indian Pediatr. 2007;44 (4):281-285.

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