Cold sores are blisters that form on the lips, around and inside the mouth, and in the nose. You can get one or several in a cluster. Also referred to as fever blisters, cold sores are usually caused by HSV-1, a type of herpes simplex virus. They may also be caused by HSV-2, the virus responsible for genital herpes.

Cold sores go through several stages. They may start out looking like red spots, and go on to form fluid-filled, red bumps. The bumps may leak and form open sores. Eventually, the sores will become crusty and scab over until they’re completely healed.

Despite a lack of scientific evidence, some people believe that apple cider vinegar can be used to treat cold sores.

One theory is that the alkaline nutrients in apple cider vinegar reduce the potency of the virus that causes cold sores to occur.

Other people believe that apple cider vinegar has anti-infective properties, possibly making it useful for treating wounds, ulcers, and sores of all kinds. This theory dates back to (460–377 B.C.), who has been referred to as the father of modern medicine.

Apple cider vinegar has been shown scientifically to have . Since cold sores are caused by a virus, not by bacteria, applying apple cider vinegar to a cold sore can’t cure it.

Apple cider vinegar is effective at removing dead skin cells, however. For this reason, it may help cold sores go away more quickly once they’ve reached the scabbing stage.

Because it has antiseptic properties, apple cider vinegar may also be beneficial at reducing the risk of secondary infection in an existing cold sore.

Anecdotal evidence often precedes scientific evidence. If you wish to try using apple cider vinegar to treat cold sores at home, here are a few methods you can experiment with:

Diluted apple cider vinegar

  1. Dilute apple cider vinegar with water in a 1:10 ratio.
  2. Soak a cotton ball in this solution and apply it to cold sores one or two times daily until the scabs heal over.

Don’t use full-strength apple cider vinegar on your skin, as it may severely burn or irritate the area, causing scarring.

Apple cider vinegar and honey

  1. Mix diluted apple cider vinegar with honey to make a paste.
  2. Apply the paste to the cold sore one or two times daily for 5 to 10 minutes.
  3. Gently dab with a soft cloth to remove. The honey may affix to the scabs, pulling them off prematurely if you remove this mixture too vigorously.

Apple cider vinegar and tea tree essential oil

Tea tree oil may help reduce inflammation and has also been shown to have an .

Don’t use this at-home treatment if you have eczema.

  1. Dilute about 5 drops of tea tree essential oil in 1 ounce of sweet almond oil or another carrier oil.
  2. Combine the diluted oil with diluted apple cider vinegar.
  3. Use this solution as a poultice to treat cold sores: Apply one or two times daily using a cotton ball, and leave it on the area for five minutes at a time.
  4. Repeat until your cold sores go away completely.

Don’t swallow tea tree oil or let it enter your mouth, as it can be toxic. Tea tree oil can irritate the skin, so it may not be appropriate for everyone.

Even though it has alkaline properties, apple cider vinegar is an acid. It should never be used full strength on skin, especially on open sores, or in sensitive areas like around the eyes, mouth, or lips. It can cause serious burns, stinging, and irritation. It can also dry out skin, causing discomfort.

If you have a cold sore, it’s important to treat it promptly. This will help stop it from spreading to other parts of your body, and to other people. The fastest way to do this may be by seeing a doctor, such as a dermatologist.

If you have a healthy immune system and don’t have atopic dermatitis, consider giving these other at-home remedies a try:

Cold sores are caused primarily by the HSV-1 virus. Apple cider vinegar is an at-home remedy that is used by some people to treat cold sores. It hasn’t been scientifically demonstrated that this is an effective treatment, however.

If you do want to try apple cider vinegar to treat cold sores, it’s important to dilute the vinegar before using it on your skin to eliminate the risk of burns or irritation.