Abreva vs Lysine: An OTC Cold Sore Drug vs a Supplement

Abreva vs Lysine at a Glance

Doses above are from the current U.S. Drug Facts or prescribing labels listed in Sources. Always follow the label on the package you buy, because store brands and formulations differ.

What Each Is

Cold sores are caused by herpes simplex virus, usually type 1, which lies dormant in nerve cells and reactivates with triggers such as sun, stress, illness or lip injury. Docosanol is a long-chain alcohol thought to interfere with the virus entering skin cells. It is the active ingredient in Abreva, sold over the counter with a Drug Facts label. L-lysine is an essential amino acid found in protein foods. The theory behind lysine for herpes is that it competes with arginine, an amino acid the virus uses, but this theory has not translated into consistent clinical benefit.

Abreva: Evidence and Directions

Sacks and colleagues (Journal of the American Academy of Dermatology, 2001) randomized people with recurrent cold sores to docosanol 10% cream or placebo, applied 5 times daily. Median time to healing in the 370 docosanol-treated patients was 4.1 days, 18 hours shorter than in the 367 placebo patients. Docosanol also shortened time to cessation of pain and other symptoms such as itching, burning and tingling. Aborted episodes occurred in 40% versus 34%, a difference that was not statistically significant. Adverse effects were mild and similar to placebo.

The Abreva label directs adults and children 12 and older to wash hands before and after applying, apply to the affected area on the face or lips at the first sign of a cold sore (tingle), rub in gently but completely, and use 5 times a day until healed. Early treatment gives the best results. Stop and ask a doctor if the sore gets worse or is not healed within 10 days.

Lysine: Evidence

The Cochrane review by Chi and colleagues (2015) included 32 randomized trials with 2,640 participants covering 19 preventive treatments. The authors failed to find any evidence of efficacy for lysine in preventing cold sores. They concluded that long-term oral antivirals can prevent cold sores, though the clinical benefit is small.

A 2017 review by Mailoo and Rampes found lysine appears ineffective for prevention or treatment at doses under 1 gram a day without a low-arginine diet, while doses above 3 grams a day appeared to improve patients’ subjective experience. The authors called for longer controlled studies and advised that people with cardiovascular or gallbladder disease be cautioned about theoretical risks of lysine supplementation.

Because supplements are not reviewed by FDA for effectiveness before sale, lysine products vary in dose and quality. Look for third-party testing if you choose to try one.

Prescription Options

For people with frequent, painful or prolonged outbreaks, prescription oral antivirals such as valacyclovir have the strongest evidence. The Valtrex label includes a 1-day cold sore regimen started at the earliest symptoms. See Valtrex vs acyclovir for details.

Practical Cold Sore Care

• Start treatment at the first tingle, itch or burning.
• Avoid touching the sore and wash hands after contact; the virus spreads by direct contact.
• Avoid kissing and sharing cups, utensils or lip products while a sore is present.
• Use lip balm with sunscreen if sun triggers your outbreaks.
• Do not use Abreva in or near the eyes.

Putting It Together: Common Situations

The scenarios below summarize what the labels and guidelines cited on this page say. They are general information, not a personal treatment plan. Your pharmacist can check the choice against your other medicines, and your clinician can tailor it to your health history.

• Tingling has just started: the Abreva label says to apply at the first sign, 5 times a day until healed.
• Hoping to prevent outbreaks with a supplement: the Cochrane review found no evidence of efficacy for lysine in prevention.
• Frequent or severe outbreaks: long-term oral antivirals had evidence of prevention in the Cochrane review; ask a clinician.

How to Read the Label Before You Buy

1. Find the active ingredient first. Brand names are often reused across products with different ingredients. The active ingredient and its strength appear at the top of the Drug Facts or Supplement Facts panel.
2. Check the “Uses” or labeled indication. A product is tested and labeled for specific uses. Using it for something else may not help.
3. Read the “Do not use” and “Ask a doctor before use” sections. They list conditions and medicines where the product may be unsafe.
4. Follow the directions for dose and duration. Note the maximum daily amount and how many days you can use it before checking with a clinician.
5. Check for duplicate ingredients. Combination products can contain the same ingredient as something else you take, which raises the risk of taking too much.
6. Note the “Stop use and ask a doctor” signs. These are the label’s own warning signs that a product is not working or is causing harm.

Common Mistakes to Avoid

• Waiting until a blister forms before starting treatment.
• Using a cold sore cream near the eyes, which the Abreva label says not to do.
• Assuming two products with similar names are interchangeable. Compare the active ingredients and strengths instead of the packaging.
• Forgetting to tell your clinician. Keep a current list of every prescription, OTC medicine and supplement you take, and bring it to appointments and the pharmacy.

FormulaCompare does not recommend one brand over another. Use the sources below to check the details for the exact product in front of you, since formulas and labels can change.

Reading the Abreva Trial Carefully

The Sacks trial is the main evidence behind Abreva’s labeled claim. A few details help put it in context. Participants started treatment themselves at the earliest signs of an episode, which is how the product is meant to be used. The 18-hour difference in median healing time is modest, and some people in both groups had episodes that never progressed past the early stage (40% with docosanol and 34% with placebo, a difference that was not statistically significant). Docosanol also shortened the time until pain, itching, burning and tingling stopped. In practical terms, Abreva may make an outbreak somewhat shorter and less bothersome when started early, but it does not prevent future outbreaks and does not remove the virus.

If You Choose to Try Lysine

Evidence does not support lysine for preventing cold sores, according to the Cochrane review. If you still decide to try it, tell your clinician, especially if you have kidney, heart or gallbladder disease, which the 2017 review flagged for caution. Read the Supplement Facts panel for the amount per serving, and look for third-party testing. Do not use lysine in place of medical care for frequent, severe or eye-area outbreaks.

When to Talk to Your Doctor or Pharmacist

See a clinician for cold sores near the eye, sores that do not heal within 10 days, very frequent outbreaks, widespread sores, sores with fever, or if you have eczema or a weakened immune system. Seek urgent care for a severe allergic reaction such as hives, facial swelling or difficulty breathing after applying a cream.

Frequently Asked Questions

Sources

• DailyMed: Abreva (docosanol 10%) cream Drug Facts label (Haleon)
• PubMed: Sacks et al., clinical efficacy of topical docosanol 10% cream for herpes simplex labialis: multicenter randomized trial (2001)
• PubMed: Chi et al., interventions for prevention of herpes simplex labialis (Cochrane, 2015)
• PubMed: Mailoo and Rampes, lysine for herpes simplex prophylaxis: a review of the evidence (2017)
• MedlinePlus: Cold sores

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