What describes pain, swelling, and redness?

The characteristics of pain, swelling, and redness are commonly associated with signs of infection. When an infection occurs, the body initiates an inflammatory response as part of the immune system's protective reaction. This response leads to the release of various chemicals that increase blood flow to the affected area, which results in swelling (edema) and redness (erythema). Pain is often a direct consequence of inflammation, as the swelling puts pressure on surrounding tissues, and the released substances can sensitize nerve endings, causing discomfort.

In contrast, an allergic reaction typically involves itching, hives, or respiratory symptoms rather than localized pain and swelling. Signs of stress might manifest physically in various ways, such as tension or headaches, but they do not specifically present as pain, swelling, and redness in the same manner. Symptoms of dehydration usually include dryness, fatigue, and decreased urine output, which also do not align with the combination of pain, swelling, and redness. Therefore, the presence of pain, swelling, and redness strongly indicates an infectious process requiring medical evaluation.