Thinking about sex or experiencing an orgasm sends some people into an uncontrolled bout of sneezing, and according to two researchers the problem may be more common than the medical profession had realised.

The doctors who investigated the link are not yet sure why sex and sneezing are linked in some people, but they suspect it is due to a faulty connection in the autonomic nervous system – the system that exercises unconscious control of, among other things, heart rate, digestion and pupil dilation.

Dr Harold Maxwell, a consultant psychiatrist at West Middlesex University Hospital in London, was first alerted to the condition when a middle-aged male patient described uncontrollable fits of sneezing whenever he thought about sex. When Maxwell and his colleague Mahmood Bhutta, a surgeon at Wexham Park Hospital near Slough set out to investigate how common the problem is they could find only one similar case in the medical literature – a case reported in 1972 of a 69-year-old man who suffered severe sneezing after orgasm. "It may also be seen as embarrassing and people perhaps don't want to talk about it," said Bhutta.

To get some indication of how common the problem is he searched internet chatrooms for people discussing the issue. This highly unscientific survey identified 17 men and women who reported sneezing immediately after having sexual thoughts and three people who sneezed after orgasm. In four of the chatroom threads, respondents also said they had suffered the same problems, but in no case did people say they sneezed not only after sexual thoughts but also after orgasm. Bhutta believes the seemingly bizarre phenomenon may be more common than doctors had previously thought.

There are other examples of unrelated events triggering sneezing. According to a large Swedish study, 25% of people sneeze in response to bright light. Bhutta said that people who have the condition simply don't see it as unusual. "They think that everybody does that," he said. Much rarer are people who sneeze after a meal when they have a full stomach. This has been identified by scientists in just two families. "Possibly that is much more common that we think as well," said Bhutta.

Both phenomena are genetically inherited.

Sneezing and sex may be linked by a faulty connection in the autonomic nervous system that controls both the sneeze reflex and sexual responses. A similar mechanism is thought to underlie the observation that in some people massaging an eyeball can dramatically slow their heart rate.

"Further investigation in this field may help us to understand the sneeze reflex in more depth, and also allow us to give explanation and reassurance to the possibly significant number of people affected by this curious phenomenon," Bhutta and Maxwell wrote in the Journal of the Royal Society of Medicine.