Prescription medication to prevent and treat cold sore outbreaks

Up to 80% of US adults may be silent carriers of the herpes virus, which can cause cold sores. Cold sores often are mild, but if you suffer from frequent or severe outbreaks, antiviral medication could help you. 


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Reviewed by Dr Roy Kedem, MD

Information last reviewed 11/04/19


What are cold sores?

Cold sores appear as tiny, fluid-filled blisters, often in clusters or patches around the mouth and lips.  A crust will form over the affected area once the blisters break.  Cold sores are frequently recurrent, although some people will only experience one outbreak in their lifetime. Subsequent outbreaks usually occur in the same location as the initial eruption, but are generally less severe and of lesser duration than the initial.


What causes cold sores?

Cold sores are usually caused by the herpes simplex virus type 1 (HSV1). Most people are exposed to HSV1 in childhood, usually from an infected friend or family member, although only about 30% will ever go on to show symptoms. As part of the herpes simplex family of viruses, HSV1 is not curable and may recur. When not active, the virus hides inside nerve cells until reemerging during the next outbreak.

Although less common, cold sores can also be caused by herpes simplex virus type 2 (HSV2), generally known as genital herpes.

Once the virus is present, many factors may contribute to triggering an outbreak,  including but not limited to the following:

  • Stress and fatigue
  • Illness, including colds and flu
  • Hormonal fluctuations during menstruation or pregnancy
  • Immune system deficiencies
  • Food allergies
  • Trauma to the mouth area, including dental work
  • Sunlight or exposure to ultraviolet lamps

How are cold sores transmitted?

Like all herpes simplex viruses, cold sores are highly contagious and transmitted through skin-to-skin contact. Cold sores caused by HSV1 are typically transmitted through mouth-to-mouth contact, such as kissing.

HSV2 (genital herpes) can also cause cold sores. In this case, transmission is usually through genital-to-mouth contact during oral sex. The reverse is also possible, with an HSV1 cold sore being transmitted to a partner’s genitals via mouth-to-genital contact.
The virus is most contagious during an outbreak, particularly when blisters are oozing, but may be transmitted even when the virus is dormant.  Avoid direct contact whenever an active cold sore outbreak is present.

You can further prevent transmission by avoiding sharing items such a toothbrush, towel, lip balm and utensils.  Washing your hands carefully after touching an affected area may also help.  Antiviral medications may reduce the rate of HSV transmission but do not eliminate the risk.  


What are the symptoms of cold sores?

Symptoms can appear from two to 12 days after initial exposure to the virus. The first sign can often be flu-like symptoms, such as fever, body aches, swollen glands in the neck, and a sore throat.

Although cold sores can last up to a month, outbreaks rarely last longer than two weeks and move through a predictable pattern of stages:

  • Day 1: Tingling stage - Tingling, itching or burning may be felt around the areas of the nose and mouth.
  • Days 2–3: Blister stage - Fluid-filled blisters begin to form.
  • Day 4: Ulcer stage (Also known as the “weeping stage” - Blisters begin to rupture, resembling an open wound. This is typically the most painful stage.
  • Days 5–8: Crusting stage - Blisters begin to dry and form a brown or yellowish crust or scab.
  • Days 9–12: Healing Stage - Scabs form and fall off until the sores are completely healed, usually without any scarring.


When should I see a doctor for my cold sores?

Cold sores normally do not require urgent medical attention and will heal on their own. Reasons to see your doctor may include:

  • A history of a compromised or weakened immune system
  • Extremely painful and severe symptoms
  • Sores which do not heal within two weeks
  • Frequent recurrences
  • Eye irritation, or a sore in or around the eye

How are cold sores diagnosed?

Your doctor will generally diagnose a cold sore visually, just by looking at it. If confirmation is desired, a swab of the sore may be taken to confirm the presence of the herpes simplex virus.

Related Conditions

Are there any complications associated with cold sores?

Although not common, complications from cold sores can arise in other parts of the body, including:

  • Eyes: If the virus is transmitted to the eyes, repeated outbreaks can lead to scarring and injury with the potential to cause problems with vision or even blindness.
  • Fingertips: Referred to as “herpes whitlow,” transmission to the fingertips is usually found in thumb-sucking children who have transferred the virus from their mouths to their thumbs.
  • Large or remote areas of the skin: In people with eczema, cold sores can spread across their body, which constitutes a medical emergency.
  • Other organs: In cases of a weakened immune system, the virus can affect other areas of the body such as the spinal cord or brain.

Certain medical conditions and treatments increase the risk of complications from HSV infections. Be sure to inform your doctor of any of the following compromises to your immune system:

  • Eczema
  • Severe burns
  • Cancer and cancer chemotherapy
  • Anti-rejection drugs for organ transplant

In these cases, your doctor may recommend regular use of antiviral medications such as Famciclovir (Famvir) to prevent complications.


What is the treatment for cold sores?

Cold sores are often mild and may not require any specialized treatment. In cases where cold sores are particularly frequent or severe, antiviral medications can be used to reduce the frequency, severity and duration of cold sore outbreaks.

Antiviral creams such as Doconazole or Acyclovir cream are applied directly to the affected area. Acyclovir and Valacyclovir are also prescribed in oral tablet form. Acyclovir (Zovirax) is most often used to treat an existing outbreak.  Valacyclovir (Valtrex) is indicated for existing outbreaks, and is also prescribed as a daily medication to help prevent recurrences.  Your doctor will decide which medication is best for you.

For those with compromised immune systems, the prescription cream Penciclovir, may be prescribed at the first sign of an outbreak to help reduce its duration. In cases of severe complications, hospital admission for IV administration of antiviral medication along with close medical supervision may be warranted.


Disclaimer: This is not medical advice. You and your physician will determine if and how you should take any medication prescribed to you following a medical consultation.

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