Cold sores are painful fluid-filled blisters that form on the borders of the lips caused by a herpes virus, most often the herpes simplex 1 virus.
Cold sores should not be confused with canker sores, which are small ulcerations in the mouth. The blisters, which are contagious, later break, ooze, and crust over before healing. Recurrences are common and can be triggered by stress, sun exposure, illness, and menstruation. Genital herpes infection (usually caused by herpes simplex 2) is a related condition and potentially may be treated in much the same way as herpes simplex 1.
What are the symptoms of cold sores?
Cold sores may appear with colds, fevers, exposure to excessive sunlight, or menstrual periods, as well as during periods of stress or illness. The sores usually disappear within two weeks. Initially, there may be tingling or prickling at the site of the cold sores even before they are visible (called the prodrome); afterward, the blisters often weep a clear fluid and form a scab. If the infection is transmitted to the eyes, it may lead to blindness.
Dietary changes that may be helpful for cold sores
The herpes simplex virus has a high requirement for the amino acid, arginine. On the other hand, the amino acid, lysine, inhibits viral replication.1 Therefore, a diet that is low in arginine and high in lysine may help prevent or treat herpes outbreaks. Several studies have shown that increasing lysine intake can reduce the recurrence rate of cold sores.2 Although people with herpes simplex reportedly consume about the same amount of arginine and lysine in their diet as do people without cold sores,3 it is conceivable that adjusting the intake of these amino acids may be beneficial. For that reason, many doctors advise people with cold sores to avoid foods with high arginine-to-lysine ratios, such as nuts, peanuts, and chocolate. Nonfat yogurt and other nonfat dairy can be a healthful way to increase lysine intake.
Nutritional supplements that may be helpful for cold sores
The amino acid, lysine, has been reported to reduce the recurrence rate of herpes simplex infections in both preliminary4 5and double-blind trials.6 7 The amount used in these studies was usually 1 to 3 grams per day, although some people received as little as 312 mg per day. In one double-blind trial, lysine supplementation (1,200 mg per day) failed to prevent recurrences better than placebo.8 However, the results of that study may have been skewed by a large number of dropouts in the placebo group who fared poorly but were not included in the analysis.
When lysine has been used for acute outbreaks, the results have been mixed. In a preliminary study, 390 mg of lysine taken at the first sign of a herpes outbreak resulted in rapid resolution of the cold sores in all cases.9 However, in a double-blind study, supplementing with 1 gram of lysine per day for five days did not increase the healing rate of the cold sores.10
Vitamin C has been shown to inactivate herpes viruses in the test tube.11 In one study, people with herpes infections received either a placebo or 200 mg of vitamin C plus 200 mg of flavonoids, each taken three to five times per day. Compared with the placebo, vitamin C and flavonoids reduced the duration of symptoms by 57%.12
Zinc preparations have been shown to inhibit the replication of herpes simplex in the test tube.13 In one study, people with recurrent herpes simplex infections applied a zinc sulfate solution daily to the sores. After healing occurred, the frequency of applications was reduced to once a week for a month, then to twice a month. During an observation period of 16 to 23 months, none of these people experienced a recurrence of their cold sores.14
Zinc oxide, the only commercially available form of zinc for topical application, is probably ineffective as a treatment for herpes simplex.15 Other forms of topical zinc can be obtained by prescription, through a compounding pharmacist. However, because an excessive concentration of zinc may cause skin irritation, topical zinc should be used only with the supervision of a doctor knowledgeable in its use.
In a preliminary trial, a piece of cotton saturated with vitamin E oil was applied to newly erupted cold sores and held in place for 15 minutes. The first application was performed in the dentist’s office. Participants were instructed to repeat the procedure every three hours for the rest of that day, and then three times daily for two more days. In nearly all cases, pain disappeared in less than eight hours. Application of vitamin E oil appeared to accelerate healing of the cold sores.16 Similar results were reported in another study.17
Application of an ointment containing propolis, the resin collected by bees from trees, has been shown to relieve genital herpes more effectively than topical acyclovir.18 It is likely that this treatment might also benefit people with cold sores, although this has not been tested. Propolis ointment should be applied four times per day.
Boric acid has antiviral activity. In a double-blind trial, topical application of an ointment containing boric acid (in the form of sodium borate) shortened the duration of cold sores by about one-third.19 However, concerns about potential toxicity have led some doctors to avoid the use of boric acid for this purpose.
A preliminary study found that people with recurrent cold sores have lower iron stores than healthy people.20 This may mean that correcting an iron deficiency might help prevent herpes outbreaks, but more research is necessary. Most people should not take iron supplements unless they have an iron deficiency, confirmed by a blood test.
Are there any side effects or interactions with cold sores?
Refer to the individual supplement for information about any side effects or interactions.
Herbs that may be helpful for cold sores
Lemon balm has antiviral properties. A cream containing an extract of lemon balm has been shown in double-blind trials to speed the healing of cold sores.21 In one double-blind trial, topical application of a 1% 70:1 extract of lemon-balm leaf cream, four times daily for five days, led to significantly fewer symptoms and fewer blisters than experienced by those using a placebo cream.22 In most studies, the lemon-balm cream was applied two to four times per day for five to ten days.
The proanthocyanidins in witch hazel have been shown to exert significant antiviral activity against herpes simplex 1 in the test tube.23 In a double-blind trial, people with acute cold sore outbreaks applied a topical cream containing 2% witch hazel bark extract or placebo six times a day for three to eight days.24 By the end of the eighth day, those using the witch-hazel cream had a pronounced and statistically significant reduction in the size and spread of the inflammation when compared to the placebo group.
Licorice in the form of a cream or gel may be applied directly to herpes sores three to four times per day. Licorice extracts containing glycyrrhizin or glycyrrhetinic acid should be used, as these are the constituents in licorice most likely to provide activity against the herpes simplex virus. There are no controlled trials demonstrating the effectiveness of this treatment, but a cream containing a synthetic version of glycyrrhetinic acid (carbenoxolone) was reported to speed healing time and reduce pain in people with herpes simplex.25
In traditional herbal medicine, tinctures of various herbs, including chaparral, St. John’s wort, goldenseal, myrrh, and echinacea, have been applied topically to herpes outbreaks in order to promote healing.
An extract from elderberry leaves, combined with St. John’s wort and soapwort (Saponaria officinalis), has been found to inhibit the herpes simplex virus in the test tube.26 However, the effect of these herbs on cold sores has not been studied.
Are there any side effects or interactions with cold sores?
Refer to the individual herb for information about any side effects or interactions.