A boil starts as a hard, red, painful lump usually about half an inch in size. Over the next few days, the lump becomes softer, larger, and more painful. Soon a pocket of pus forms on the top of the boil. These are the signs of a severe infection:
1. The skin around the boil becomes infected. It turns red, painful, warm, and swollen.
2. More boils may appear around the original one.
3. A fever may develop.
4. Lymph nodes may become swollen.