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.

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.⁴ 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.⁵ In most studies, the lemon-balm cream was applied two to four times per day for five to ten days.

The amino acidlysine has been reported to reduce the recurrence rate of herpes simplex infections in both preliminary^{6 , 7} and double-blind trials.^{8 , 9} 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.¹⁰ 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.¹¹ 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.¹²

Vitamin C has been shown to inactivate herpes viruses in the test tube.¹³ 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%.¹⁴

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.¹⁵ Similar results were reported in another study.¹⁶

The proanthocyanidins in witch hazel have been shown to exert significant antiviral activity against herpes simplex 1 in the test tube.¹⁷ 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.¹⁸ 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.

Zinc preparations have been shown to inhibit the replication of herpes simplex in the test tube.¹⁹ 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.²⁰

Zinc oxide, the only commercially available form of zinc for topical application, is probably ineffective as a treatment for herpes simplex.²¹ 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.

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.²² However, concerns about potential toxicity have led some doctors to avoid the use of boric acid for this purpose.

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.

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.

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.

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.²³

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.

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.²⁴ 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.

Caution: It is likely that there are many drug interactions with St. John's wort that have not yet been identified. St. John's wort stimulates a drug-metabolizing enzyme (cytochrome P450 3A4) that metabolizes at least 50% of the drugs on the market.²⁵ Therefore, it could potentially cause a number of drug interactions that have not yet been reported. People taking any medication should consult with a doctor or pharmacist before taking St. John's wort. 

In traditional herbal medicine, tinctures of various herbs, including St. John’s wort, chaparral, goldenseal, myrrh, and echinacea, have been applied topically to herpes outbreaks in order to promote healing.