Skin boils are usually caused by infections from bacteria. The most common bacteria are staphylococcus aureus or group A streptococcus. Both of these are treated with antibiotics. Methicillin resistant staphylococcus aureus (MRSA) is a bit harder to treat, but essentially looks the same as other forms of staph. Boils can also come from fungi.
Boils hurt and itch. They're usually diagnosed by the way they look, which are like big pimples. The symptoms can be summed up as a red, swollen bump surrounded by red, irritated skin. Eventually, there will be one or more small white heads (pustules) in the center. Once in a while, boils heal without forming a white head.
Be warned, these pictures are not for the faint of heart. Boils are hard to look at, but much harder to live with. Many of these boils were submitted as spider bites. Most of them are not spider bites; our skin has natural openings around hair follicles where bacteria can sneak in and cause an infection. Whether originally spider bites or not, these pictures illustrate typical skin boils.
Treating a skin boil depends on the cause of the boil. In some cases, treatment will require the intervention of a healthcare provider. However, there are certainly some first aid tips you can try at home to make boils more tolerable and encourage them to heal on their own.