Mouth sores are tiny round and shallow structures red in color. It can be painful and may last for 5-7 days. Mouth sores may recur several times. In severe cases it can cause fever or chills. It produces tingling sensation in the cheeks before mouth sores develop. Mouth sores can reduce one’s ability to chew, eat and drink and sometimes it restricts your speech also. It can be either single bumps or cluster of blisters. Mouth sores occur anywhere in the oral cavity but largely occurs in the lips and inside the cheeks. It produces irritation and discomfort in the mouth.