Which of the following is a side effect common to numerous cough medications?

Nausea is a common side effect associated with many cough medications, particularly those that contain antitussives or other active ingredients such as opioid derivatives. These medications can affect the gastrointestinal system, leading to symptoms like nausea or vomiting. This side effect arises from the medication's action on the central nervous system, as well as potential irritation effects on the stomach.

While dizziness is also a known side effect of some medications, it is not as universally common across the wide range of cough medications as nausea is. Rash is typically associated with allergic reactions or specific drug sensitivities, and while increased breathing rate can occur due to various factors, it is not a standard side effect of cough medications. Thus, nausea stands out as a prevalent side effect across many different cough treatments.