This leads to the potential for great damage to the sneezer if the sneeze is not expelled; i.e., the sneeze is "internalized" or kept contained within the sneezer's air passages. There are several potential methods through which the "internalized" sneeze can lead to significant injury:
- The lungs may be exploded; this generally leads to difficulty breathing, which can result in death.
- The diaphragm (the muscle that compresses the lungs like an air pump to allow breathing) can have the lungs forced through it, which leads to difficulty breathing, which can result in death.
- The diaphragm may become "vapor locked" - this is similar to a hydraulic lock situation, in which the forces (or fluids) on either side of a membrane (in this case the diaphragm) are in equilibrium without room for expansion, locking the membrane into a fixed, immobile position; in the event that the diaphragm becomes locked in place, this leads to difficulty breathing, which can result in death.
- In rare cases, the head may explode, either internally or (more rarely) externally, which nearly always results in death.
Many readers will be familiar with Neanderthal Man. This was a humanoid species (Homo neanderthalensis or Homo sapiens neanderthalensis) that lived between 130,000 and 30,000 years ago. While their disappearance has typically been explained by extinction, cross-breeding with modern Homo sapiens, or that they actually never were a different species from modern Homo sapiens and simply transformed into modern human form, new discoveries have identified "sneeze inhibition" (holding in their sneezes) as the actual cause for demise of the species.
A recent discovery of frozen Neanderthal remains in a remote region of Siberia includes a significant number of near-complete individuals, who, through the sub-freezing temperatures, were found encased in a layer of ice, preserving their soft tissues. Autopsy has revealed that these Neanderthals suffered from a range of the previously mentioned maladies that may occur as a result of sneeze internalization, primarily the "exploded lung" issues (although the two diaphragm issues did occur in lower percentages: about 75% of those found had exploded lungs consistent with "internalized sneeze injuries," 15% had vapor-locked diaphragm issues, 8% had lungs that had punctured the diaphragm, 1.3% had internal head explosions, 0.3% had external head explosions, and 0.4% had other injuries, some of which could be explained by internalizing a sneeze, while others indicate externally applied injuries, such as being hit in the head with a large club).
Nearby caves had early cave drawings consistent with Neanderthal stories, but with some interesting images never before observed (see example image to the right). These images have been interpreted by leading scholars to indicate that the Neanderthal community had achieved a higher social system than previously believed, and that the "sneeze" was considered a vulgar expression. Apparently the potential to spread disease was recognized early in this society. Additionally, the larger size of the nose of Neanderthal man must have made the sneezes much more violent than modern man. Together, this must have led the Neanderthals to the desire to avoid expelling their sneezes at all cost; unfortunately, the "at all cost" eventually cost them their race, as the entire species was wiped (so to speak) from the face of the earth, with the exception of a small remnant that has recently been featured in Geico insurance commercials (unfortunately mis-labeled "cave men" instead of "Neanderthals" or "Homo neanderthalensis").
In short, you should take a lesson from our long-lost brethren: don't hold in your sneeze! It's not worth the potential damage that the tornadic-force winds can wreak on your body.