A young man happens to spot an ex-girlfriend he's trying to avoid. Why does his mouth become dry?

The sensation of a dry mouth in a stressful or anxiety-inducing situation, such as spotting an ex-girlfriend you're trying to avoid, is commonly attributed to the body's stress response. In this case, the body activates the "fight or flight" response, which triggers various physiological changes to prepare the individual for potential danger. One of the effects of this response is the release of stress hormones, such as adrenaline and cortisol.

When stress hormones are released, they can affect the body in different ways, including suppressing the production of saliva. This reduced saliva production can lead to a sensation of dryness in the mouth. Additionally, stress and anxiety can cause a person to breathe through their mouth instead of their nose, which can further contribute to dryness.

To alleviate this dry mouth sensation, the young man could try taking slow, deep breaths through his nose to calm his body's stress response. Additionally, staying well-hydrated by drinking water can help in maintaining a more comfortable level of saliva production.