What are hematomas?

Hematomas are specifically defined as a collection of blood outside of blood vessels, usually resulting from trauma to the skin or tissues. When blood vessels rupture, blood seeps into the surrounding tissues, leading to discoloration and swelling, which is commonly recognized as a bruise. The visible change in skin color is due to the presence of pooled blood, which can be seen through the skin.

Understanding this concept helps clarify why the other options are not applicable. Skin irritations caused by allergies do not involve blood or bruising, while scars formed after the healing process refer to the skin's response to injury and repair, not the acute collection of blood. Normal skin features might include things like freckles or birthmarks but do not pertain to the presence of blood outside of blood vessels, as seen in hematomas. Thus, identifying hematomas accurately as bruises aligns correctly with their medical definition and understanding.