Lysine for Prevention of Cold Sores in Children
There is insufficient high-quality evidence to recommend a specific dose of L-lysine for preventing cold sores in pediatric patients, and the available research shows conflicting results regarding its effectiveness.
Evidence Quality and Limitations
The provided guidelines 1 address unrelated conditions (MRSA infections, HIV-related opportunistic infections, pneumonia, and cardiac surgery) and contain no recommendations for lysine use in herpes simplex virus prevention. The only relevant evidence comes from research studies with significant limitations 2, 3, 4, 5.
Research Evidence on Lysine for Herpes Simplex
Studies Showing Potential Benefit
- A 1978 multicentered study reported that 312-1,200 mg of lysine daily (in single or multiple doses) appeared to accelerate recovery and suppress recurrence in 45 patients with frequently recurring herpes infection 4
- A small 2005 pilot study in adults using a topical L-lysine combination product showed resolution in 40% by day 3 and 87% by day 6, though this was an open-label study without pediatric-specific data 2
Studies Showing No Benefit
- A 1984 double-blind, placebo-controlled trial using 400 mg three times daily (1,200 mg/day total) in 21 adults found no substantial benefit for treatment or prophylaxis of recurrent herpes simplex 3
- A 1980 double-blind crossover study using 1,000 mg daily in 65 adults showed no overall effect on recurrence rate, though significantly more patients were recurrence-free during lysine treatment (p=0.05), suggesting only certain patients may benefit 5
Critical Gaps in Pediatric Evidence
No pediatric-specific dosing studies exist in the provided evidence. The research cited 2, 3, 4, 5 exclusively studied adult populations, making direct extrapolation to children problematic. A 2024 review noted lysine supplementation for growth in children but did not address herpes prevention or provide specific antiviral dosing 6.
Clinical Approach in Absence of Guidelines
Given the lack of pediatric guidelines and conflicting adult data:
- If considering lysine supplementation despite limited evidence: Adult studies used 1,000-1,200 mg daily 3, 4, 5, but pediatric weight-based dosing would be more appropriate
- Safety considerations: Lysine supplements are generally considered clinically safe with side effects limited to gastrointestinal symptoms, though excessive intake can cause amino acid imbalance 6
- Alternative approach: Standard antiviral therapy (acyclovir, valacyclovir) has established efficacy and pediatric dosing for herpes simplex prevention, unlike lysine