What condition is characterized by excessive oil production leading to greasy skin?

The condition characterized by excessive oil production leading to greasy skin is seborrhea. This disorder results from an overproduction of sebum by the sebaceous glands, which can cause the skin to appear shiny or greasy. Seborrhea is commonly found on the scalp and can also occur on the face and other areas with oil glands, leading to symptoms such as flaking or scaling.

In contrast, acne is a condition that is often related to oil production too, but it specifically involves the clogging of pores and the presence of pimples, blackheads, and cysts rather than just greasy skin. Rosacea is primarily known for causing redness and visible blood vessels, along with bumps and pimples, but does not inherently cause excessive oil production. Dermatitis is a broader term for skin inflammation, which may present with a variety of symptoms including redness and itching but does not specifically denote excessive oiliness.

Overall, seborrhea is distinct in its straightforward manifestation of excess oiliness, making it the correct answer in this context.