What is aspiration in the context of first aid?

Aspiration refers to the occurrence when foreign materials, particularly liquids like water or food, enter the airway and lungs instead of being swallowed correctly. This can lead to serious complications, including respiratory distress or aspiration pneumonia, as the body's defense mechanisms may become overwhelmed. In the context of first aid, recognizing the signs of aspiration is critical because it can affect a person's ability to breathe and require immediate intervention.

The other options do not accurately define aspiration in the first aid context. An injury generally involves physical harm to the body rather than the act of inhaling substances. Signs of shock typically relate to the body's response to a significant loss of blood or fluids but are not specifically about aspiration. A reaction to medication can involve various side effects but does not pertain to the process of aspiration, which deals explicitly with inhaling substances into the lungs.