If you find yourself sneezing at the same time every day, your nose and your internal clock are conspiring together to tickle you at just that moment.
Sneezing is essentially just an immune response meant to clear mucus out of the sinuses.
Most of the time, it is an involuntary reaction to some kind of irritant: dust, pollen or other tiny particles floating in the air.
But our biological clocks – dictated by circadian rhythms – move in concert with the immune system, prompting timely sneezing bouts, experts explain.
Every time we go to sleep, our immune systems get a reset. Like the rest of our bodies, the system downshifts into a lower gear during this period during which we are fighting fewer outside invaders.
‘It turns out that there is an endogenous circadian rhythm in the immune system and generally it tends to rev up in the later stages of sleep,’ says Dr Michael Smolensky.
Dr Smolensky, a chronobiologist at the University of Texas, explains that the body has a sense of when it is about to wake up and greet the day – and all of the allergens that come with it.
These symptoms actually start ramping up while we are still asleep, but we do not notice until we wake.
People who suffer from bouts of sneezing at exactly the same time every day, Dr Smolensky says, typically have the problem first thing in the morning.
Importantly, this is also the first time in several hours that they encounter sun.
Sneezing can in fact be a symptom of a ‘sun allergy’ Dr Smolensky says.
‘I use the term loosely though. People get outside, they’re looking to the east at the sunrise, and it can very often provoke the thought of sneezing,’ he explains.
You could also call this the ‘photic sneeze reflex,’ or photoptarmosis, or autosomal dominant compelling helio-opthalmic outburst (ACHOO) syndrome.
ACHOO syndrome only affects between one and two percent of people, and it is genetic.
Chronic sinusitis – long-term, recurring inflammation of the sinuses – are more likely to sneeze more in general, but also to have sneezes that follow a temporal pattern, says Dr Mahboobeh Mahdavinia, an allergy and immunology specialist at Rush University Medical Center.
Those who sneeze more ‘have more secretions and inflammation to start with and…there is evidence that these people are more prone to circadian changes of inflammatory mediators,’ she says.
In other words, our immune systems fluctuate dependent upon where we are in our sleep cycles, and our sleep cycles can be altered by whatever is going on with our immune systems.
We know that the immune system revs up at the start of the day, so more sneezing is most likely at this time, but Dr Mahdavinia says that our levels of secretions fluctuate throughout the day, and vary for each individual, so our sneezes do too.
A ‘vicious cycle’ could well lead to daily sneezes at odd times, Dr Smolensky says.
People prone to sneezing are also more likely to have their nasal congestion wake them in the night, disrupting their sleep, leading to inflammation and mucus production, which leads to sneezing, and so on.
A secondary factor to that circle, he says, is irritability, which comes from sleeplessness and makes people less tolerant of allergy and irritation symptoms, Dr Smolensky says, and more likely to notice their daily reactions.
