A skin abscess is a localized collection of pus that forms within the skin due to infection. It often appears as a swollen, red, and painful lump. Common causes include bacteria, such as Staphylococcus aureus, entering the skin through cuts or insect bites. Treatment typically involves draining the pus and may require antibiotics to eliminate the infection. It's important to keep the area clean and monitor for signs of worsening infection, such as increased redness or fever. If left untreated, a skin abscess can lead to more serious complications.