Cold sores are small blisters that appear in or around the mouth. They usually show up on or next to the lips. They can also appear on the nose, the chin or inside the mouth. Most people know the tingle that warns one is on the way.

There is no cure, but there is plenty you can do. Good care can ease the discomfort and help stop the virus spreading to others. This guide covers what causes cold sores, what sets them off and how to look after your skin while one heals.

What causes cold sores

Cold sores are caused by the herpes simplex virus, often shortened to HSV. HSV type 1 usually causes cold sores. HSV type 2 causes most cases of genital herpes. Either type can cause cold sores, genital herpes or both.

The virus is very common. According to healthdirect information on cold sores, about 8 in 10 people are infected by adulthood. Most people catch it when they are young and carry it for life. The virus can lie dormant, so some people never get a cold sore at all.

That means you can carry the virus without knowing it. It also explains why cold sores tend to come back in the same spot. The virus stays in the body between outbreaks. Certain triggers can then wake it up again.

How a cold sore develops

A cold sore tends to move through three stages. First comes an itchy or tingling feeling, sometimes with a raised spot. Next, small painful blisters filled with fluid form. Finally the blisters crust over and heal within a few days.

Some people also feel unwell during an outbreak. Fever, headache, sore throat and swollen glands can come with a cold sore. Most cold sores heal on their own within about two weeks. They usually do not leave a scar.

Not every sore or spot near the mouth is a cold sore. Other skin conditions can look similar in the early stages. Our guide asking what’s my rash runs through some common skin reactions. If you are unsure, a pharmacist or GP can take a look.

Common triggers

Triggers vary from person to person. Healthdirect lists fatigue, menstrual periods and emotional upset or stress. Illness and hormonal changes can also bring one on. So can sunburn and skin damage from strong sun, cold or wind.

Knowing your own triggers helps you plan. If strong sun sets yours off, a lip balm with sunscreen and a hat are worth the habit. If tiredness is the trigger, sleep becomes part of your skin care. Some people find stress is the main culprit, so relaxation techniques can help.

How cold sores spread

Cold sores are highly contagious, even when blisters are not present. The virus spreads through direct contact with a cold sore or with saliva and other body fluids. Kissing and close skin contact are common ways it passes on. Sharing drink bottles, cutlery, towels or toothbrushes can spread it too.

Simple ways to protect others

• Avoid kissing and close contact while you have a cold sore.
• Wash your hands after touching the sore or applying cream.
• Do not share cups, cutlery, towels, flannels, razors or toothbrushes.
• Keep your cold sore cream for your own use only.

Extra care is needed around babies, young children and pregnant people. People with a weakened immune system are also at higher risk. The virus can cause severe illness in these groups. An infection in a newborn should always be managed by a doctor.

Looking after a cold sore at home

Try not to lick, poke or pick at the sore. Touching it can spread the virus to your fingers or eyes. When applying a cream, dab it on gently rather than rubbing. Follow the instructions on the packet for any product you use.

Ice can help ease the pain. Paracetamol may also help with discomfort, and a doctor can advise on other options. Eating well, getting enough sleep and managing stress all support your body while it heals. These habits may also help you avoid some triggers in future.

Help from the pharmacy

Antiviral creams and ointments are available from pharmacies without a prescription. They work best in the first few days, when the tingle starts or a raised spot first appears. A pharmacist can also supply a single dose antiviral tablet without a script. Cold sore patches and antiseptic ointments are other options they may suggest.

You may see lysine promoted as a way to prevent cold sores. Healthdirect notes there is no evidence that it works. It is better to speak with a pharmacist about proven options. They can help you choose what suits you.

Cold sores and dental visits

A cold sore can be uncomfortable during dental work, since the mouth is stretched open for a while. It is a good idea to let your dentist know before an appointment if you have one. They can advise whether to go ahead or rebook. This applies to routine check ups as well as treatments like dental fillings.

The same goes for longer procedures. If you are planning treatment under sleep dentistry, mention any cold sore when you confirm the booking. If you wear aligners, wash your hands before taking them out or putting them back in while you have a cold sore. Our guide on Invisalign vs braces covers the day to day care each option needs.

When to see a doctor

For most people, cold sores heal with pharmacy products and self care. See a doctor if a sore is large, deep or very painful. You should also see one if a sore is not healing, is spreading or you have more than one. Signs of infection such as redness, pus or fever also need checking.

Some situations need prompt attention. If a cold sore is near your eye, see a doctor immediately, as it can cause serious problems. People with a weakened immune system should also seek advice. If you get cold sores often, a doctor can talk to you about ways to manage them.

Frequently asked questions

How long does a cold sore last?

Most cold sores heal on their own within about two weeks. The blisters crust over before they heal. They do not usually leave a scar. See a doctor if one is not healing.

Can I spread a cold sore when I cannot see it?

Yes. Cold sores are highly contagious, even when blisters are not present. Avoid sharing cups, cutlery and towels with others. Wash your hands after touching your lips or any sore.

When should I use an antiviral cream?

Antiviral creams work best early. Start when you first feel the tingle or see a raised spot. They are available from pharmacies without a prescription. Follow the directions on the pack.

Is a cold sore near the eye serious?

It can be. The virus can spread to the eye and cause serious complications. See a doctor straight away if a cold sore appears near your eye. Avoid touching the sore and then your eyes.

This article is general information only and is not medical advice. Please speak with your doctor or a qualified health professional about your own health.