The amino acidlysine has been reported to reduce the recurrence rate of herpes simplex infections in both preliminary^1,2 and double-blind trials.^3,4 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.⁵ 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.⁶ 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.⁷

The amino acidlysine has been reported to reduce the recurrence rate of herpes simplex infections in both preliminary^8,9 and double-blind trials.^10,11 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.¹² 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.¹³ 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.¹⁴

Because shingles is caused by a herpes virus, some doctors believe that lysine supplementation could help people with the condition, since lysine inhibits replication of herpes simplex, a related virus. However, lysine has not been shown to inhibit Varicella zoster, nor has it been shown to provide any benefit for people with shingles outbreaks. Therefore, its use in this condition remains speculative.