How to know if something is infected

How can you know if an injury is infected?  Patients are often concerned when wounds don't heal right away and this causes them to make needless visits to the doctor or emergency room.  My little dog scratched my arm while I was giving her a bath (isn't she cute). Below is a picture of the scratch wound that is about 6 days old.

Is this scratch infected?

If you said no, it is healing well, you would be correct. Even though it is still swollen around the scratch and it is obviously red and a little warm, these are signed of normal skin healing. I can picture my white blood cells and monocytes racing to the area to deal with bacteria from the scratch. The redness and swelling are an inflammatory response that my immune system is producing to contain the bacteria and turn over new cells.

Signs of infection would be redness that continues to extend outside the wound that is worsening over time.  The swelling wouldn't stay the same, it would expand day by day. The cut it self might start oozing under the scab that is forming. If any of that occurred, it would be time to get it checked out.

As we get older (ahem!) we heal more slowly. Cuts and lacerations might take weeks to heal, rather than the days of healing that occurred when we were youths. This is normal also.

The best thing to do when you get a scratch or cut is to wash it with regular soap and water as soon as possible. Studies have shown that antimicrobial soaps do not offer any advantage and sterile water is not needed. Cover the wound with a bandaid or clean gauze.  If it is a deep cut that continues to bleed, that is a sign that sutures (stitches) might be needed. It is is important to remember that animal scratches or bites do have bacteria that can cause infections so if it becomes very swollen, red and tender it may need a doctor visit. Otherwise just let your body do its magic and heal.

This was originally posted 9/22/16 and revised today