L-Lysine

Tier 2 — promising · Cold sores · Collagen · Immunity

An essential amino acid studied for preventing cold sores (herpes simplex). Evidence is mixed — some trials show reduced recurrence, others show no benefit. Theory: lysine competes with arginine, which herpes virus needs to replicate. Also supports collagen synthesis and calcium absorption. Very safe at standard doses. Most useful at higher doses (3 g/day) during outbreaks.

Dose: 500–3,000 mg/day for cold sore prevention; take on empty stomach; avoid high-arginine foods during outbreaks