Laughter may not be the best medicine after all and could even harm us, new research has revealed.
Despite the known benefits of chuckling, for some people it has proven to be more dangerous than expected.
One woman with racing heart syndrome collapsed and died after a giggling fit, say researchers.
And laughing "fit to burst" has been found to cause possible heart rupture, a torn gullet and epileptic seizures.
A quick intake of breath during laughing can provoke an asthma attack, while some people have suffered from incontinence and even hernias.
Researchers from Birmingham and Oxford Universities used data from 1946 to the present day to study the benefits of laughing on the human body.
During one test clowns were sent into hospitals to entertain patients.
And the results showed a dose of "genuine laughter" for a whole day could help shed the kgs by burning 2,000 calories.
And 36 per cent of would-be mums undergoing IVF treatment got pregnant after a visit from the red-nosed jokers, compared to just 20 per cent in a control group.
Tittering was also linked with lowering blood sugar in diabetic patients and reducing arterial wall stiffness, which helps relieve tension.
The researchers say their findings challenge the view that laughter can only be beneficial but do add that humour in any form carries a "low risk of harm and may be beneficial".
"It remains to be seen whether sick jokes make you ill, dry wit causes dehydration or jokes in bad taste [cause] dysgeusia (distortion of sense of taste)," they said.
The paper was published in the Christmas edition of The British Medical Journal.
- DAILY MAIL