What is mouth redness? Redness around the mouth is a common symptom of infection or injury, or it could be a sign of an underlying condition of another part of the body. Mouth redness may be caused by pathogens, such as bacteria, viruses and fungi, which inflame the mucous membranes of the mouth. It may occur in conditions affecting parts of the mouth, such as the lips, tongue or gums, or in association with more generalized conditions, such as human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) or leukemia. Only in rare situations does mouth redness result in a serious or life-threatening situation. Cold sores, or “fever blisters,” that surface on the skin around the mouth result from the herpes simplex virus. Blisters within the mouth may be a sign of hand-foot-and-mouth disease (HFMD), which can be caused by several types of viruses. Fungal infections, such as candida, may also cause mouth redness. Depending on the cause, redness may occur only in one area or it may affect the entire mouth. Trauma caused by excessive teeth brushing can lead to redness of the mouth, which may damage the gums and cause inflammation, swelling, or canker sores. Ill-fitting dentures may also cause sores and mouth redness. Any type of trauma to the mouth, lips or tongue can result in mouth redness as a result of inflammation and swelling around the site of injury. Mouth redness is rarely associated with a medical emergency. Seek immediate medical care (call 911) if your redness is associated with bleeding that cannot be stopped, pale skin or pallor, loss of teeth, high fever (higher than 101 degrees Fahrenheit),swelling in your lips or tongue, or difficulty breathing, If your mouth redness is persistent or causes you concern, seek prompt medical care.