There are several signs that may indicate an overgrowth of bad skin bacteria on the skin: Acne breakouts: An overgrowth of bad bacteria can contribute to the development of acne by producing substances that cause inflammation in the hair follicles. Skin infections: If you develop symptoms of a skin infection, such as redness, swelling, warmth, and pain, this may indicate an overgrowth of bad bacteria on the skin. Foul odor: If your skin has a strong, unpleasant odor, this may indicate an overgrowth of bad bacteria. Itching or burning: If your skin is itchy or burning, this may indicate an overgrowth of bad bacteria, as well as other skin problems such as eczema or psoriasis. Dry, flaky skin: If your skin is dry and flaky, this may create a environment where bad bacteria can thrive.