A cold sore is an open blister caused by the herpes simplex 1 virus. The sore typically forms around the outside of the mouth and dries into a scab. Since cold sores are caused by a virus, they have no cure and will usually clear up on their own within a week. Luckily, cold sores can easily be covered up, so you don't have to be self-conscious during the healing process.
Apply a thin layer of cold sore ointment directly onto your cold sore. These over-the-counter ointments cannot cure the sore, but they have antibiotics and topical pain relievers to prevent infection and discomfort. If you don't have any ointment, use a thin layer of petroleum jelly instead. The petroleum jelly will form a smooth barrier over the bumpy cold sore and make it easier to cover up. Use a cotton swab to apply it rather than using your finger. If you use your finger and dip it back into the jelly, you can contaminate the entire container with the virus. Try to keep the ointment or petroleum jelly directly onto the sore itself and avoid getting them on the areas of skin surrounding the sore. The thick materials that help coat your cold sore can clog your skin pores and potentially cause breakouts.
Use a liquid makeup concealer that matches your skin tone to cover up your cold sore. You'll want to start applying the concealer immediately after smoothing on the ointment or petroleum jelly. If the cold sore isn't lubricated, the concealer will not evenly cover it and may sink into the crevices of the sore, making it look even more unattractive. Apply concealer onto a cotton swab (to prevent contaminating the entire container of concealer with the virus), then dab the concealer directly onto the cold sore without rubbing it in. Once the concealer is applied to the surface of the sore, use your finger to gently tap it until the edges of the concealer are evenly blended. Make sure not to blend the concealer by rubbing it or you could accidentally smear it off.
If your cold sore is directly on your lip, you can also use lipstick to help minimize the sore's appearance. After you've applied the ointment or petroleum jelly and the concealer, use a lipstick in your preferred color. If possible, choose an extra-creamy formula that will keep the sore from drying out and becoming more noticeable. Once again, make sure not to apply the lipstick directly onto your lips straight from the tube. You can use a cotton swab, but it may leave white particles in the lipstick. Purchase a cheap lip brush that that you can throw away to smooth on lipstick or simply cut off the top portion of the lipstick and place it into a small container. Use your finger to apply it directly onto your lips, then discard the remaining lipstick left in the container.