Fever blisters or simply put cold sores are caused by herpes simplex type 1 – a virus that lives in a dormant state in your body even after the cold sores have been treated. Hence, herpes simplex outbreaks as and when you are exposed to triggers such as hormonal changes, weak immune system, trauma, stress, and overexposure to sunlight. Fever blisters can be really painful and are often accompanied with tingling, burning, inflammation and swelling. Antiviral ointments and medications over a long period of time can have serious side effects. Here are some effective home remedies to cure fever blisters that work well when you start using them as soon as the first symptoms appear.