Cold sore (herpes simplex virus): Learn the Causes, Symptoms and Treatment

Picture of Cold sore



Cold sores are small blisters that develop on the lips or around the mouth. They are caused by the herpes simplex virus and usually clear up without treatment within 7 to 10 days.

You will not have any symptoms when you first become infected with the herpes simplex virus. An outbreak of cold sores may happen some time later.

Cold sores often start with a tingling, itching or burning sensation around your mouth. Small fluid-filled sores will then appear, most commonly on the edges of your lower lip.

Cold sores, sometimes called fever blisters, are clusters of small blisters on the lip and outer edge of the mouth. They are caused by the herpes simplex virus.

Cold sores (also known as fever blisters) are pretty common and lots of people get them.

What’s the difference in the types?

  • On the face, herpes simplex type 1 is more likely to recur than type 2. 

How can it recur?

  • Once you have caught this virus, it hides in nearby nerve sheaths and can sometimes reactivate. There are other viruses that also hide and come back later: for example chickenpox/shingles, glandular fever and cytomegalovirus (CMV) but they do not cause cold sores.

How did I get my cold sores?

  • You catch it the first time by being kissed by someone who has cold sore virus on his or her face. This may have been when you were too young to remember  or just the other day. It is only caught by direct skin contact, not through sharing cups, cutlery, towels, etc.

How is it passed on?

  • You pass it on by kissing someone when you have a cold sore or when you feel that one may be coming. If the other person does catch it from you, sores appear on the bit of body you kissed. Oral sex is a common way of passing on cold sores from one person’s mouth to another person’s genitals (genital herpes).

Can anyone get cold sores?

  • Yes, but you can’t give cold sores to someone who already gets them. This means that you cannot give this virus back to the person you caught it off, even on a different part of his/her body.

How many people get cold sores?

  • Cold sores are very common. About six in ten people carry the virus. However, most of them don’t know because they have never noticed any symptoms. Only a quarter of the people who catch this virus will notice any symptoms at all.

What is a cold sore like?

  • First a small red patch appears
  • A blister or cluster of blisters develops. You may just get a shallow ulcer inside your mouth.
  • The blister bursts, leaving a small raw area.
  • The raw area begins to heal and scab.
  • Moving your mouth can cause the scab to crack. This will delay healing, so keep the skin soft and moist – see our self-help ideas below.
  • Picking at the scab will also delay healing

Can cold sores make you ill?

  • Occasionally, when a person first catches it, he/she gets ulcers inside the mouth and throat as well as, or instead of, the usual sores on the lip. There could be a fever and other flu-like symptoms. A painkiller can help: aspirin, ibuprofen or paracetamol – always follow the instructions on the packet.

Can cold sores ever be serious?

  • Rarely. A few unlucky people get them too often. Antiviral tablets or medicine can be prescribed by a doctor or see our self-help ideas below.
  • People who have areas of broken skin (like eczema), or people who have other serious illnesses, must be careful during their first infection as it can spread over all the area of broken skin. Rarely, people develop erythema multiforme following each cold sore; they may be given antiviral tablets.
  • Even more rarely, a cold sore may reappear in your eye. If one eye is tingling and sore or red your GP may do a fluoroscein stain, this is to see if the cause is herpes simplex virus. If it is, you may be referred to a specialist eye hospital.

What triggers a recurrence?

  • Triggers vary from person to person: try and learn what provokes your cold sores and then you can try and prevent them.
  • Common reasons for recurrences are tiredness, illness, stress, being run down, menstruation, too much alcohol or the ultraviolet rays from sunlight or sunbeds.

Can I prevent cold sores?

Look after yourself. Avoid any triggers you have identified.

  • Get enough sleep.
  • Improve your diet.
  • Try taking a multi-vitamin & mineral pill.
  • If sunlight is one of your triggers, use a good quality sun block.

What can I do if a cold sore is starting to appear?

  • Apply well-wrapped ice for 90 minutes to cold the area, not cause frostbite.
  • Use a herbal cream made with lemon balm mint extract (melissa officinalis) such as Lomaherpan (formerly called LomaBrit). The active ingredient prevents the virus getting into the skin cells. It is available from the HVA for £6 for 5g tube (with £1 for p&p) on our shop page.