Within seconds of eating chocolate, I sneeze three or four times. I’m in my mid-80s and this has only just started. Is it an allergy and, if so, why has it taken so long to develop?
Alan Gardner, Sheffield.
I first came across this phenomenon during my training, while working in the nose clinic at the Royal Brompton Hospital in London — since then, I have seen a surprising number of patients with the issue.
You’ll be relieved to hear that it is not believed to be an allergy — so you can still eat chocolate. That’s because the sneezing isn’t accompanied by any other symptoms of an allergic response, such as itching in or around the mouth or hives (and allergy tests carried out on my own patients with chocolate reactions confirmed this).
Instead, it’s thought to be caused by a reflex — possibly a variant of the photic sneeze reflex, where sneezing is triggered by exposure to the sun or bright lights.
Fact: It’s thought sunlight-induced sneezes are due to crossed wires in the trigeminal nerve. It is believed that, sometimes, signals about sunlight cross over into the nose branch, which leads to them being mistaken for a tickle in the nose.Something similar occurs with chocolate.
This genetic quirk, passed down through families, affects around one in five people and has long been a source of intrigue. In Ancient Greece, Aristotle asked why the sun provoked sneezing — and there are even tales of knights in armour sneezing when setting their eyes on pretty maidens.
It’s thought sunlight-induced sneezes are due to crossed wires in the trigeminal nerve. This large and complex nerve has three branches that transmit information to the brain from the eyes, nose and jaw.
It is believed that, sometimes, signals about sunlight cross over into the nose branch, which leads to them being mistaken for a tickle in the nose — and a sneeze is triggered.
Something similar may occur with chocolate.
It contains theobromine, a bitter-tasting compound known to suppress dry coughs by acting on the vagus nerve — another nerve that carries crucial information between the body and brain.
In this case, erroneous cross-talk between the vagus nerve and the trigeminal nerve may somehow set off a sneeze.
It is also possible flavonoids, antioxidants found in cocoa beans, may be involved — some stimulate the production of nitric oxide, a chemical that helps widen blood vessels.
Did you know? Chocolate contains theobromine, a bitter-tasting compound known to suppress dry coughs by acting on the vagus nerve — another nerve that carries crucial information between the body and brain.
This prompts me to suggest that perhaps, in rare cases, chocolate fuels a brief rush of blood in the capillaries within the nasal lining — this is interpreted by the brain as a tickle, and a sneeze ensues.
Why this should become an issue at this point in your life is unclear, though it might depend upon chocolate type and purity. For example, the milk in milk chocolate may interfere with the absorption of some of the sneeze-inducing constituents.
If this is the case, then dark chocolate may be more likely to make you sneeze.
This is speculation but, if it tallies with your experience, eating milk chocolate — in moderation, of course — may make you less likely to sneeze.
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