Which of the following conditions is characterized by painful vesicular eruptions?

The condition characterized by painful vesicular eruptions is genital herpes. This viral infection, caused by the herpes simplex virus, primarily manifests as clusters of blisters (vesicles) that appear on or around the genitalia. These vesicles are often accompanied by significant pain, itching, and discomfort, making the outbreak quite distressing for those affected.

Unlike the other options, which either do not involve vesicular eruptions or are not skin-related conditions, genital herpes specifically presents with the hallmark symptoms of painful vesicular lesions. Asteatosis refers to a lack of oil or lipids in the skin, leading to dryness, while chloasma is a condition causing pigmentation changes in the skin, often seen in pregnancy. Diathermy is a medical treatment that uses heat and does not relate to skin eruptions. Therefore, genital herpes is distinctly recognized for its painful vesicles, making it the correct choice.