Whenever you have a direct contact with the sunlight, you should apply a sun screen having an SPF value of 15 or greater. Even if it's cloudy, UV levels can still be a major issue in bringing on a cold sore.

Injury to the lips can trigger cold sores. Minimize the potential for lip damage associated with chapping by applying a moisturizing lip balm. You can use a lip balm that contains a sun screen having an SPF. Studies show that using lip balm helps prevent facial infection. There are also specialty lips balms designed to prevent dryness, prevent triggers and inhibit viral replication in people who have already suffered from cold sores. These lip balms claim to dramatically reduce recurrence. Make sure to use a strong SPF sunscreen lip balm when outdoors.