Which condition presents as a benign round oval patchy rash on the trunk and upper limbs?

Pityriasis rosea is characterized by a distinctive presentation that often begins with a "herald patch," which is a solitary, round, pink or tan oval lesion. Following this initial patch, multiple smaller lesions appear, typically on the trunk and upper limbs, creating a pattern that can resemble the shape of a Christmas tree. This rash is generally asymptomatic or mildly itchy and tends to resolve on its own within several weeks to a few months, making it a benign condition.

Understanding this, the specificity of pityriasis rosea lies in its unique distribution and appearance, which contrasts with the other conditions listed. Psoriasis often presents as well-defined, red, scaly plaques that can cover larger areas and be associated with other symptoms. Eczema (atopic dermatitis) typically appears as itchy, inflamed patches that can vary in color and are often accompanied by dryness or crusting, and it can affect various areas, not limited to the trunk and upper limbs. Contact dermatitis results from skin exposure to allergens or irritants, leading to localized rashes that may have a more inflammatory appearance, often with vesicles and oozing.

Pityriasis rosea's benign nature, specific rash morphology, and predictable course make it the correct