L-Lysine

L-lysine for cold sores

Cold sores are caused by the herpes simplex virus. Lysine is thought to work by competing with arginine, an amino acid the virus needs. Research results are mixed: some studies found that taking around 1 to 3 g a day reduced how often cold sores came back, while others found little effect. It is not a cure, and antiviral creams or tablets from a doctor work better during an outbreak.

L-lysine for mouth ulcers

Common mouth ulcers (canker sores, aphthous ulcers) are different from cold sores and are not caused by the herpes virus, so there is little reason to expect lysine to help. Most mouth ulcers heal by themselves within two weeks. Frequent ulcers can be linked to stress, injury from teeth or braces, or low iron, B12 or folate. See a dentist or doctor about any ulcer that lasts more than three weeks, especially if you smoke or chew tobacco or betel nut.

Food sources of lysine

Lentils (dal), beans, fish, meat, eggs, milk and yoghurt are all good sources. A typical Bangladeshi diet with dal and fish provides plenty of lysine, so supplements are rarely needed for nutrition alone.

Is a lysine supplement safe?

At usual doses, lysine is well tolerated, though it can cause stomach upset. People with kidney or liver disease should not take lysine supplements without medical advice, and pregnant or breastfeeding women should ask a doctor first, as safety data are limited. Choose L-lysine tablets from a brand with third-party testing and check the dose per tablet, which ranges from 500 mg to 1,000 mg.

Preventing cold sores

Sunlight, stress, illness and tiredness commonly trigger cold sores. Use a lip balm with SPF outdoors, avoid kissing and sharing cups or towels during an outbreak, and wash your hands after touching a sore. Antiviral creams work best when applied at the first tingle.