Rosh Emergency Medicine Practice Test 2025 - Free Emergency Medicine Practice Questions and Study Guide

A burn that affects only the epidermis is classified as a first-degree burn. This type of burn is characterized by damage limited to the outermost layer of skin, which leads to symptoms such as redness, minor swelling, and pain. The skin remains intact and typically heals within a few days without leaving scars.

First-degree burns result from mild sunburns or brief contact with hot surfaces, illustrating that the injury is superficial and does not extend deeper than the epidermis. Due to their limited severity, these burns generally have a good prognosis and are the least serious among burn classifications.

In contrast, second-degree burns involve not just the epidermis but also the underlying dermis, leading to blisters, more intense pain, and longer healing times. Third-degree burns penetrate through both the epidermis and dermis, destroying these layers and sometimes affecting deeper tissues, which results in a significantly altered appearance and requiring more extensive treatment. Fourth-degree burns are even more severe, reaching into muscle and bone, often necessitating surgical interventions or reconstructive procedures.

Thus, the defining feature of a first-degree burn is its exclusive involvement of the epidermis, making it the correct answer.