On a few occasions, I've literally choked on the "juice" of candy like Skittles or peppermints. I don't choke on the candy itself, just the liquid, which causes me to panic and then not to be able to breathe. I end up making this noises of someone not being able to get air into their lungs. What causes this? I've also noticed it when I start chewing a piece of gum. When this first happened, I had a respiratory infection; I would cough so hard I wouldn't be able to catch my breath. Now it only seems to happen with the liquid to candy. What could this mean?

T.R.

That alarming, whooping noise you make is due to laryngospasm. Your vocal cords are slamming shut in an effort to prevent liquid from entering your lungs. Unfortunately, the vocal cords must be open for you to breathe, so slammed-shut cords are incompatible with life. In reality, you would not actually suffocate; at worst, you would pass out, and then your cords would relax, and you would be able to breathe again.

While the cords are in the closed position, you nevertheless are trying your best to inhale. In fact, your chest wall muscles and diaphragm are probably making mighty efforts to suck in some air. The noise you make is due to small amounts of air being sucked through tightly closed vocal cords. Have you ever made a noisemaker by putting two strips of paper together, pursing your lips together at one end and blowing? (This works better with thin plastic than paper -- the paper gets too soggy!) Same concept: You are forcing air through a tight space, creating a high-pitched noise.

Back to your question. Why does this happen only with the saliva you produce while sucking on a sweet? To understand this, you need to recognize that sweets are a relatively recent innovation, speaking on an evolutionary timescale. Neanderthals didn't suck Skittles, in other words. As we evolved, our larynx (voice box) descended in the neck; this was critically important, as it enabled the development of human speech. Unfortunately, this also brought the larynx closer to the esophagus, thus introducing the risk of aspiration to every swallow. (Aspiration is the medical term for the accidental passage of food or liquid into the windpipe.)

We usually don't aspirate our food and drink. There are a number of protective mechanisms that guard us against aspiration. During a swallow, the larynx rises (moving it away from the esophagus), the vocal cords close, the false vocal folds also close (these are bands of tissue immediately above the vocal cords) and the epiglottis (a leaf-shaped cartilage) moves in such a manner as to block food and drink from hitting the vocal cords.

But that occurs only during an actual swallow. When you suck on candy, you produce a steady flow of thin saliva, which trickles down the back of your throat. This is different than a true swallow, in which you propel a ball of something (be it chewed-up food or a volume of liquid) safely past your airway and into your esophagus. True swallows we can handle -- we've been doing that for millions of years. A steady trickle of saliva ... that's a different story.

What's happening is this: The flow of sugary liquid is escaping the usual defense mechanisms until it reaches your vocal cords, perhaps even your windpipe. At that point, you sense that something really bad is about to happen (your lungs would not do well if flooded with a sugar-saliva combo), and your cords slam shut to protect your airway -- voila, laryngospasm.