Most people who become infected with the virus that causes cold sores never develop symptoms. However, they still may be contagious to others, even without blisters.
For people who do develop signs and symptoms, a cold sore usually passes through several stages, which include:
- Tingling and itching. Many people feel an itching, burning or tingling sensation around their lips for a day or two before cold sore blisters erupt.
- Blisters. Small fluid-filled blisters typically break out along the border where the outside edge of the lips meets the skin of the face, although the blisters can also occur around the nose or on the cheeks.
- Oozing and crusting. The small blisters may merge and then burst, leaving shallow open sores that will ooze fluid and then crust over.
Symptoms can vary, depending on whether this is your first outbreak or a recurrence. During first-time outbreaks, some people also experience:
- Sore throat
- 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. Young children are also more likely to spread the virus to other locations on their bodies, such as their fingers or around their eyes.
When to see a doctor
Cold sores generally clear up without treatment. However, see your doctor if:
- You have a weakened immune system
- The cold sores don't heal within two weeks
- Symptoms are severe
- You have frequent recurrences of cold sores
- You experience irritation in your eyes
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. However, either type can cause sores in the facial area or on the genitals.
You get the first episode of herpes infection from another person who has an active lesion. Shared eating utensils, razors and towels, as well as kissing, may spread HSV-1. Oral sex can spread HSV-1 to the genitals and HSV-2 to the lips.
While cold sores are most contagious when they are oozing fluid, the virus can be transmitted to others even during times when you have no blisters.
Once you've had an episode of herpes infection, the virus lies dormant in nerve cells in your skin and may emerge again as an active infection at or near the original site. Recurrence may be triggered by:
- Exposure to the sun
About 90 percent of adults worldwide — even those who've never had symptoms of an infection — test positive for evidence of the virus that causes cold sores.
People who have weakened immune systems are at higher risk of complications from the virus. Medical conditions and treatments that increase your risk of complications include:
- Severe burns
- Cancer chemotherapy
- Anti-rejection drugs for organ transplants
In some people, the virus that causes cold sores can cause problems in other areas of the body, including:
- Fingertip. Both HSV-1 and HSV-2 can be spread to the fingers. Children who suck their thumbs may transfer the infection from their mouths to their thumbs.
- Eyes. The virus can sometimes cause pinkeye (conjunctivitis). If ulcers develop on the eye itself, it can result in vision problems and even blindness.
- Widespread areas of skin. People who have a skin condition called eczema are at higher risk of cold sores spreading all across their bodies. This can become a medical emergency.
- Other organs. In people with weakened immune systems, the virus can also affect organs such as the lungs, liver and brain.
Your doctor may prescribe an antiviral medication for you to take on a regular basis, if you develop cold sores frequently or if you're at high risk of serious complications.
To help avoid spreading cold sores to other people or to other parts of your body, you might try some of the following precautions:
- Avoid skin contact with others while blisters are present. The virus spreads most easily when there are moist secretions from the blisters.
- Be careful about touching other parts of your body. Your eyes and genital area may be particularly susceptible to spread of the virus.
- Avoid sharing items. Utensils, towels, lip balm and other items can spread the virus when blisters are present.
- Keep your hands clean. Wash your hands carefully before touching another person when you have a cold sore.