Cold sores — also called fever blisters — are a common viral infection. there is a tiny, fluid-filled blisters on and around the lips. After the blisters break, a scab forms.

Cold sores spread from person to person by close contact, such as kissing. They're usually caused by herpes simplex virus type 1 (HSV-1), and less commonly herpes simplex virus type 2 (HSV-2). Both of these viruses can affect our mouth or genitals and can be spread by oral sex. Cold sores are contagious even if you don't see the sores.

Symptoms

A cold sore usually passes through several stages:

• Tingling and itching. Many people feel itching, burning or tingling around the lips for a day or so before a small, hard, painful spot appears .
• Blisters. Small fluid-filled blisters typically erupt along the border of lips. Sometimes they appear around the nose or cheeks or inside the mouth.
• Oozing and crusting. The small blisters may merge and then burst, leaving shallow open sores that ooze and crust over.

some other symptoms include:

• Fever
• Painful gums
• Sore throat
• Headache
• Muscle aches
• Swollen lymph nodes

Children under 5 years old may have cold sores inside their mouths and the lesions are commonly mistaken for canker sores. Canker sores involve only the mucous membrane and aren't caused by the herpes simplex virus.

Causes

Cold sores are caused by certain strains of the herpes simplex virus (HSV).

HSV-1 usually causes cold sores.

HSV-2 is usually responsible for genital herpes. But either type can spread to the face or genitals through close contact, such as kissing or oral sex. Shared eating utensils, razors and towels might also spread.

Cold sores are most contagious when we have oozing blisters because the virus easily spreads through contact with infected body fluids. But you can spread the virus even if you don't have blisters. Many people who are infected with the virus that causes cold sores never develop signs and symptoms.

Once you've had an episode of herpes infection, the virus lies dormant in nerve cells in your skin and may emerge as another cold sore at the same place as before. Recurrence may be triggered by:

• Viral infection or fever
• Hormonal changes, such as those related to menstruation
• Stress
• Fatigue
• Exposure to sunlight and wind
• Changes in the immune system
• Injury to the skin

HOMOEOPATHIC TREATMENT

Actually homeopathic remedies for cold sores are meant to boost your immune system. its help  to fight back against cold sores with a strong mind and body. The following are a few homeopathic remedies that have worked to minimize the appearance and pain associated with cold sores:

Natrum Muriaticum 

Nat Mur is commonly used for things like water retention, swelling, etc. It makes sense that it would reduce the swelling and overall appearance of blistering cold sores. 

Sepia 

Very useful medicine for blister formation around the mouth which oozes discharge.