Urban mythology claims that each year, a certain number of spiders crawl into out mouths while we are asleep and are consequently eaten. While the exact number of spiders that we are supposed to eat varies widely, the common theme remains the same and the stories usually suggest that there is nothing we can do to prevent this from happening.
|Spider silk is one of most amazing chemicals in nature, being both incredibly light and having a tensile strength that is far greater than steel. In fact, the silk of the golden orb weaver (not shown above) is 6 times stronger than steel and is 10 times more efficient at absorbing energy than military-grade kevlar, being tough enough to capture bats and small birds!|
Whereas it is doubtful that we could stop spiders from crawling or lowering themselves into our mouths if they wanted to (we are asleep afterall), there is actually no need as a spider would not be interested in creeping down our throats, so that in fact, we have nothing to worry about whatsoever!
This is mainly due to the content of our breath, which is warm, humid and has a much higher carbon dioxide to oxygen ratio than 'normal' air does. If a spider was crawling towards our mouth, it would sense such conditions when we breathed over it and would actively avoid them since they signal that the conditions within are mouth are harsher than those outside. Imagine, for example, smelling smoke coming from your living room - even if you couldn't see or feel the flames, you would know that something was wrong and that there may be a danger in the room. Thus, you would most likely avoid going in!
For similar reasons it is unlikely that a spider would want to enter your mouth and, if one was on your face, would probably turn tail and run once it came close enough to feel your breath!