Laughter matched drops for dry-eye relief, according a BMJ report on a study by Sun Yat-sen University, Xiamen University and Queen’s University Belfast.  

Results showed that laughter exercise was non-inferior to 0.1% sodium hyaluronic acid in alleviating dry eye disease (DED) symptoms, said authors. “Additionally, we found that laughter exercise appeared to improve tear film stability and the meibomian gland function.” 

Researchers assessed the efficacy and safety of laughter exercise as a treatment for 299 patients aged 18 to 45 with symptomatic DED. Participants were randomised to one of two groups receiving laughter exercise or artificial tears (0.1% sodium hyaluronic acid). 

The laughter group was instructed to vocalise phrases such as “hee hee hee, hah hah hah” 30 times in a five-minute session, repeated four times daily for eight weeks. Although both groups showed significant improvements in ocular surface disease index scores, the laughter group experienced a mean improvement of −10.5 points, while the control group showed an improvement of −8.83 points. 

The biological mechanisms of laughter exercise on DED are unclear, but a 2022 paper concluded positive emotions in non-human animals can induce tear secretion through the release of oxytocin, which could be triggered by laughter.