Buy a bar of chocolate with 90% cocoa to get home and put the first piece in your mouth to have that bitter and pleasant hit that many seek. But what you find is a series of sneezes as if it were an allergy. If you have identified with this microstory, you are not allergic to cocoa, but you are part of a curious minority victim of a neurological “short circuit” that science has studied and that could directly connect with Neanderthals.
A crossing of cables. Sometimes the body gives us many surprises, such as sneezing when we get a bit of sun after leaving the house. But if we focus on chocolate, the reality is that We are not talking about an immune response with histamine involved. The explanation most accepted by the scientific community lies in the trigeminal nerve.
The trigeminal nerve is one of the most important nerves we have and is responsible for transmitting sensitive information from the face to the brain. In the event that we eat dark chocolate, especially with a purity greater than 70%, compounds such as theobromine and caffeine intensely stimulate taste receptors.
The theory. What is being proposed right now is that in certain people this signal is so powerful that the trigeminal nerve becomes “confused.” In this way, when passing close to the optic nerve and the respiratory tract, the brain interprets this explosion of bitter and intense taste as a nasal irritant or a powerful visual signal, triggering the sneeze to “expel” the supposed threat.
The solar connection. As we have mentioned previously, there is a well-documented phenomenon in which 25-30% of the population sneezes when looking at bright light like that of the Sun. This is what is known as a photic sneeze reflex and science has strong support for stating that it is due to hyperexcitability in the visual cortex.
Well, chocolate sneezing seems to be a variant or “first cousin” of this photic reflex. In fact, it is quite likely that if a person sneezes on chocolate, they will also do so when leaving the house on a sunny day. Both are failures in the filtering of signals in the trigeminal nerve.
Neanderthal heritage. As explained by biologist Gerry Ward in an archived blog postthis trait is not a random error that exists in the population, but is a direct inheritance in our genetic material, and goes one step further by pointing out that it may come directly from Neanderthals.
The hypothesis on the table is that, in prehistoric times, this reflex acted as a defense mechanism to clean the respiratory tract against unknown tastes or smells that could be dangerous. In this way, what today is a great nuisance when eating a simple dessert, 40,000 years ago could have been a great evolutionary advantage that marked the survival of certain individuals.
It’s more complex. Although dissemination almost always falls into great simplicity, genetic data is complex. In this case, Ward’s theory placed the responsible gene in the chromosome 11but later data from 23andMe, the famous genetic analysis company, identified specific markers associated with this phenomenon on chromosome 12. But this later changed, since studies on the photic reflex pointed to variations in the chromosomes 2 and 3.
This suggests that the trait is polygenic since there is not a single “switch” for sneezing, but rather several genetic components that increase the probability of suffering from it.
How many suffer from it. Although a priori you may hear that this is a ‘problem’ that is present in 30% of the population, the reality is that this figure corresponds to the photic reflex related to sunlight.
The sneeze caused specifically by dark chocolate is much more unique, since, according to data collected by 23andMe among its users, only about 1% of the population reports systematically sneezing after consuming dark chocolate. In this way, we are facing a select club within the largest group of those who sneeze for light.
Images | Tetiana Bykovets Towfiqu barbhuiya
GIPHY App Key not set. Please check settings