The butterfly effect is a term used in chaos theory to describe how small changes to a seemingly unrelated thing or condition (also known as an initial condition) can affect large, complex systems.
For other uses, see Boil (disambiguation). A boil, also called a furuncle, is a deep folliculitis, infection of the hair follicle. It is most commonly caused by infection by the bacterium Staphylococcus aureus, resulting in a painful swollen area on the skin caused by an accumulation of pus and dead tissue. Boils which are expanded are basically pus-filled nodules.
These are the signs of a severe infection: 1  The skin around the boil becomes infected. 2  More boils may appear around the original one. 3  You develop a raised temperature. 4  Nearby lymph nodes (glands) may become swollen.