Stretch marks are called as such because they develop when your skin has stretched significantly in a short period of time. Common reasons for developing stretch marks are pregnancy, rapid weight gain and steroid usage. The marks, called striae, look like thin stripes and are often found on the buttocks, hips and stomach. Stretch marks are areas of unbroken skin; they are not open wounds. Like any other area of your body, stretch marks can become infected if bacteria or fungi thrives on your body.
Look at the color of your stretch marks. According to Medline Plus, a service of the National Institutes of Health, stretch marks may be red or sliver in color; the shade tends to fade over time. Your stretch marks may be infected if you see areas of bright red, even in marks that you've had for a long time.
Check your striae routinely for unusual growths or other occurrences that could indicate infection. Staphylococcus infections, impetigo or cellulitis, common types of skin infection, may start with a sore, boil, scratch or pus-filled mass, according to MayoClinic.com. If your marks develop open sores, scratches that become inflamed or leak fluids, they may be infected.
Take your temperature. Signs of serious skin infections that have progressed rapidly can include a fever.
Keep a record of your overall health, including any soreness you've noticed where your stretch marks are located, along with muscle aches or chills. These can all indicate an infection is brewing somewhere in your body.