Cold sores

Medical information

Written and reviewed by a team of doctors. Dr Fox is regulated by the CQC, GPhC, & MHRA.

What are cold sores?

Cold sores are sores on the lips caused by the herpes virus. Aciclovir tablets and cream are antiviral treatments which reduce the severity and duration of cold sores. Tablets may be a more convenient treatment than cream.

Aciclovir cream and tablets

Aciclovir cream or tablets are supplied by Dr Fox to treat recurrent cold sore on the lips. Some people have cold sores which come up time and again in the same place on the lips. These cold sores usually break out at times of stress or in response to triggers such as fatigue, cold weather, or strong sun or wind exposure. In some cases cold sores come up without an obvious trigger. Early treatment with either aciclovir cream or tablets will usually reduce the severity and the duration of the sore.

Treatment with either tablets or cream should be started as soon as symptoms start, even at the tingling stage, before a sore breaks out on the skin surface. Typically there is tingling at the site of a cold sore for 24 to 48 hours before a sore breaks out. If treatment is started more than a few days after the onset of symptoms, it is likely to be ineffective.

Dose of aciclovir

Apply aciclovir cream or take one aciclovir 200mg tablet 5 times daily (every 4 hours during the day time, leaving out a dose overnight). Tablets can be swallowed whole or dissolved in water and are continued for 5 days (25 tablets total in one course). Cream is usually continued for about the same length of time, until the sore has almost completely healed. Both treatments are equally effective.

Higher strength aciclovir tablets are made (aciclovir 400mg and 800mg), but are not available from Dr Fox. Higher strength tablets and higher dose treatments are usually reserved for severe or frequent infections, first infections, or infection in immunodepressed patients. In these circumstances a face-to-face consultation with a doctor is advised. Some patients take aciclovir long term to prevent outbreaks of cold sores or genital herpes. This requires prolonged or high dose treatments, and is not available from Dr Fox.

Cautions

Aciclovir cream can be used by almost all people, unless they are sensitive to it. Most people can take aciclovir tablets, even with other prescribed medication. People with significantly reduced kidney function may require reduced doses of aciclovir tablets.

Pregnancy and breast feeding: The manufacturers of aciclovir cream and tablets advise avoidance in pregnancy and breast feeding. This is precautionary advice, and there is no evidence of harm to developing pregnancies or breast-fed infants.

Side effects of aciclovir

Most people do not experience significant side effects. Of those who experience side effects the most common (affecting between 1 in 10 and 1 in 100) are dizziness and headache or nausea, vomiting, diarrhoea and abdominal pain, or fatigue and fever. People who have been diagnosed with a neurological illness should consult their doctor before taking aciclovir tablets.

People who are affected by drowsiness should not drive or operate machinery.

A full list of cautions and side effects can be found in the manufacturer's patient information leaflets.

• Aciclovir Cream
• Aciclovir Tablets

Aciclovir 10gm cream and aciclovir 200mg tablets are prescription only medicine – our doctors will issue the prescription online direct to our pharmacy.

Cold sores and genital herpes

Cold sores are sometimes called the 'kissing disease'. Spread of herpes is more likely when there is an open sore on the surface of the skin. This is the time when the virus is being shed from the surface of the skin and is most likely to be spread from one person to another.

Cold sores are caused by the same types of herpes viruses which cause genital herpes infections. Herpes virus infection can spread by direct contact from the lips to the genital region, or vice versa. Cold sores can also be spread from the lip region of one person to the lip region of another and from the genital region of one person to the genital region of another.

Is it a cold sore?

People who have had cold sores before usually recognise the symptoms, mainly because the sores come up in exactly the same place each time. Most cold sores usually last a week or 10 days before completely healing, usually without scarring. If symptoms are not improving after a few days, or are worsening, or there is a high fever and generalised flu like symptoms, consult a doctor.

People who have not had cold sores before, and have symptoms for the first time, should consult a doctor.

Sores starting around the nose that are yellow sticky and crusty, and spread out over a period of a few days are likely to be impetigo, not cold sores. Impetigo is a bacterial infection treated with antibiotics, not aciclovir, which is an antiviral.

Typical cold sore

Cold sores break out repeatedly in the same place. The skin often tingles and burns before the sore breaks open. Cold sores usually heal completely within 10 days without scarring.

Below is a photograph of a typical cold sore.

Dr Fox supplies Aciclovir on prescription – you are required to answer a short medical questionnaire before your order can be completed.

Authored 18 February 2015 by Dr Tony Steele
Last updated 3 October 2019

Reviewed by Dr B. Babor
Last reviewed 04 January 2017