Caused when an infection develops within a hair follicle, a boil usually starts out as a red, tender lump. Gradually, the boil fills with pus, growing larger and more painful until it ruptures and drains. A boil can develop anywhere on the skin, but usually occurs on armpits, buttocks, face, neck or thighs. These areas are prone to boils because they are most likely to produce sweat or generate friction.
When a cluster of boils forms a connected area of infection under the skin, that condition is called a carbuncle, often appearing on the back of the neck, shoulders or thighs. Carbuncles cause a deep, more severe infection then single boils. If you develop a carbuncle, healing takes longer than a single boil and scarring may occur.
A boil often has the following symptoms:
- Red, swollen or painful bump under the skin
- Whitish tip in the center
Typically a small boil will build up and drain in five to seven days. See a doctor immediately if a boil:
- Appears on an infant
- Develops on the face, groin, rectum or spine
- Causes fever or severe pain
- Limits movement
- Results in swelling, red streaks or any discoloration in nearby skin
Types of Boils
There are four types of boils:
- Furuncle or Carbuncle
An abscess in the skin caused by the bacterium Staphylococcus aureus; a furuncle usually involves one hair follicle. Carbuncles form abscesses on several hair follicles.
- Cystic Acne
Most common on the face, especially during the teen years, cystic acne forms when oil ducts become clogged and infected.
- Hidradenitis Suppurativa
With hidradenitis suppurativa, multiple abscesses form under the armpits and in the groin area, usually because of local inflammation of the sweat glands. Often the involved sweat glands will need surgical removal to stop the inflammation.
- Pilonidal Cyst
This unique kind of abscess occurs in the crease of the buttocks. Pilonidal cysts often begin as tiny areas of infection in the hair follicles and can become very painful.
For small boils, apply warm compresses for 20 to 30 minutes, three to four times daily. After the boil drains, wash the skin with antibacterial soap. Cover the area with a clean bandage to promote healing and prevent spreading.