When herpes simplex virus attacks your mouth region and causes tiny but painful blisters on lips, gums, etc. the condition is known as cold sores. The worst thing about cold sores is that it is highly contagious. Some of the most common causes of cold sores are stress, flu, fever, cold, fatigue, menstruation, injury, calcium deficiency, and weakened immune system. Common symptoms include appearance of fluid filled blisters around mouth, tingling sensation, pain, etc. There are plenty of home remedies that can effectively cure cold sores which have no side effects unlike the over the counter medications available for cold sores. Here are some best home remedies for cold sores.