Your child has what looks like a pimple, boil or spider bite. How do you know if it’s actually a drug-resistant staph infection, or MRSA, which needs immediate medical treatment?

First, take a good look at the bump. Is it red and swollen? Does your child wince when you touch it? If so, there’s a good chance it may be MRSA.

“Whenever there’s an infection of the skin where there’s lumps, bumps or pus, you should suspect staph,” says Stanley Deresinski, MD, a professor of infectious diseases at the Stanford School of Medicine. “And whenever you suspect staph these days, you should suspect MRSA.”

MRSA bacteria can invade wherever there’s a cut or opening in the skin: skinned knees, razor cuts, infected acne or hair follicles, scrapes from a skateboard fall, an insect bite that’s been scratched, even places where a uniform or equipment chafe the skin.

In the past, MRSA was generally found only in hospitals and long-term care facilities. But over the last couple of decades, more and more people have been infected from a different strain of the germ, known as community-acquired MRSA.

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Unlike normal staph infections, MRSA is resistant to regular front-line antibiotics, such as methicillin. (In fact, MRSA stands for methicillin-resistant staphylococcus aureus.) The infection is contagious and can progress substantially within 24 to 48 hours, sometimes becoming resistant to treatment after 72 hours — another reason that parents need to be alert for any sign of it.

How to recognize a MRSA infection

A MRSA infection will usually be marked by:

  • redness
  • a hard, swollen lump
  • a pus-filled bump
  • a lump that’s warm to the touch
  • pain

If you or your child experiences these signs or symptoms, especially if they are accompanied by a fever, call the doctor and ask to be seen immediately. Most MRSA skin infections can easily be cleared up with antibiotics as long as they're treated promptly. The doctor may also want to lance the site to relieve the pain, which may also help clear the infection. 

Go to the emergency room if you or your child has a painful, lumpy skin infection along with any of these problems:

  • A fever above 101.3 F or below 95 F
  • An unusually fast heart rate
  • Fast breathing or difficult breathing
  • Mottled skin
  • Unusual swelling
  • Confusion or disorientation

These are signs and symptoms of a systemic MRSA infection, meaning the bacteria may have spread to the bloodstream and caused blood poisoning. This is a medical emergency.

If you or your child shows symptoms of a systemic MRSA infection, the hospital should give you or him a rapid DNA PCR test for MRSA. MRSA spreads very fast once it gets in the blood, so it’s urgent to get treated before it causes abscesses in organs and leads to sepsis, an inflammation of the whole body that can be life-threatening.

A highly contagious infection

About one in three people carry the staphylococcus bacteria in their nose and about two in 100 carry MRSA without developing an infection, according to the Centers for Disease Control and Prevention (CDC). The bacteria can, however, cause an infection if it gets into a cut in the skin.

“Staph infection is common in kids because the nose runs, and they have their fingers up their nose,” says Lisa Asta, MD, of Casa Verde Pediatrics in Walnut Creek, California. “Kids also fall down and skin themselves a lot more.”

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MRSA, says Asta, can strike anyone “from a little baby whose umbilical cord has just come off all the way up to [your] big high school sports player. It doesn’t discriminate based on age, race or socio-economics.”

Since MRSA is highly contagious, it’s important to teach your child or teen not to share personal items and to wash his hands frequently.

“Just the mechanism of flushing with water is amazingly fabulous,” says Asta. “The best thing about washing is that it reduces the bacterial burden on your body.”

The CDC puts hand and body washing at the top of its prevention tips:

  • Clean your hands and body regularly, especially after exercising
  • Avoid sharing personal items such as towels, razors, bars of soap, uniforms, and clothing
  • Cover cuts and keep them clean and dry until healed
  • Put a clean towel between your skin and shared equipment like weight training benches

If your child has an active MRSA infection that has been treated by a physician, you should:

  • Avoid direct contact with open wounds and bandages
  • Use gloves, then an alcohol gel after changing the bandages on an infection site
  • Wash clothes, sheets and towels regularly and dry them completely

Attention swimming pool, hot tub and sauna fans: MRSA does not survive for long in chlorinated water — but that doesn't mean you can't get it from locker room benches, towels and hand rails, or from skin-to-skin contact. Take precautions.

Related: The Down and Dirty on Hot Tubs

Ana Manley-Black, J.D., is a former immigration attorney and a freelance health and medical writer whose stories have appeared in Healthday, Consumer Health Interactive, and other media.