Cold sores are caused by the herpes simplex virus (HSV-1) and often surface during times of stress or weakened immunity, or from excess exposure to sunlight, insufficient sleep and poor diet. Several studies found the amino acid lysine was an effective treatment for cold sores. Those study results, along with millions of word-of-mouth success stories, have made lysine the best-selling natural cold sore remedy ever.

In one review of 1,543 people who supplemented with lysine daily for six months, 84% reported that lysine prevented cold sore recurrence and 92% reported improved symptoms. While the average healing time without treatment is 6-15 days, 83% of treated participants said their sores healed in five days or less.

In another study at the Indiana University School of Medicine, a double-blind, placebo-controlled study found lysine could reduce occurrence, severity and duration of cold sores. Here, 27 adults were given lysine three times a day for six months. Compared to the placebo group, the lysine group had an average of 2.4 fewer cold sores, and reported significantly reduced symptoms and healing time.

Echinacea is also gaining ground as an effective treatment for cold sores. Due to its antiviral properties, echinacea is generally accepted as an effective treatment against another virus, the common cold. Researchers at the University of Ottawa theorized echinacea’s antiviral properties might make it effective against HSV-1. Indeed, after laboratory tests, the researchers confirmed that Echinacea pallida and Echinacea purpurea had potent antiviral activity against HSV-1.

Sources: Dermatologica. 1987;175(4):183-90; J Antimicrob Chemother. 1983 Nov;12(5):489-96; Cochrane Database Syst Rev. 2000;44(2):CD000530; Planta Med. 2002 Sep;68(9):780-3