What types of medical conditions are classified as 'trauma'?

Trauma is specifically defined as physical injury or damage to the body resulting from an external force. This encompasses a wide range of injuries, including fractures (broken bones), lacerations (cuts), burns, and contusions (bruises). The key element in this definition is the involvement of an external force, which distinguishes trauma from other medical conditions.

In contrast, the other options represent different types of medical issues that do not fall under the trauma category. Allergies, asthma, and chronic illnesses are more related to internal physiological responses and long-term health conditions rather than acute physical injuries. Respiratory infections and skin diseases involve pathological processes rather than injuries caused by external forces. Lastly, mental health disorders and substance abuse pertain to psychological and psychiatric health, which again does not relate to physical trauma caused by external agents. Therefore, the classification of trauma clearly aligns with injuries resulting from external forces, like those indicated in the correct answer.