An abscess is a buildup of fluid under the skin that feels like a soft lump. Sometimes the fluid drains out through a hole in the skin.

A sterile abscess (also called an injection abscess) is an abscess that happens after an injection (shot). Unlike other types of abscesses, there is no infection. Most sterile abscesses go away with basic home care. If needed, the health care provider will drain the fluid from the abscess.

Follow the health care provider's directions for:

• Any medicines to give or ointments to use.
• Giving medicine for pain, such as acetaminophen (Tylenol^® or a store brand) or ibuprofen (Advil^®, Motrin^®, or a store brand). Follow the package directions for how much to give and how often. Don't give ibuprofen to babies under 6 months old.
• Cleaning the abscess and whether to cover it with a bandage.
• Using warm, wet compresses to help the abscess drain. 
• Whether your child should soak the abscess in warm (not hot) water. 

Your child has:

• New or worsening redness, swelling, or pain
• Fluid draining from the abscess for longer than a few days
• Fever or chills
• Red streaks around the abscess

Why do some people get a sterile abscess after a shot? A sterile abscess can form if:

• The medicine that is injected doesn't absorb into the body and causes irritation.
• Someone is allergic to the medicine that was injected.
• Something in the medicine causes irritation at the injection area.

Does a sterile abscess leave a scar? Usually not. But sometimes a hard lump can be felt in the area where the sterile abscess was.