When you have a cold sore, the biggest mistakes involve touching it, spreading the virus to others or to other parts of your own body, and doing things that slow healing or trigger future outbreaks. Cold sores are contagious from the first tingle until the scab falls off and the skin looks completely normal, a process that takes one to two weeks. Knowing what to avoid during that window protects both you and the people around you.
Don’t Touch the Sore
This is the single most important rule, and the hardest to follow. Touching a cold sore transfers the herpes simplex virus (HSV-1) to your fingers, and from there it can reach your eyes or other parts of your body. Herpes in the eye, called ocular herpes, can cause pain, blurred vision, and in severe cases, damage to the cornea. The Cleveland Clinic notes that the path is simple: you touch an open sore on your lip, then rub your eye, and the virus moves with you. The same mechanism can cause herpetic whitlow, a painful infection of the fingers.
If you do touch the sore, whether applying cream or accidentally, wash your hands immediately with soap and water. Keep hand sanitizer nearby as a backup. Resist the urge to pick at the blister or peel the scab. Breaking the scab open exposes fresh viral fluid and can also leave a scar.
Don’t Kiss or Have Oral Contact
Cold sores are most infectious within the first 24 hours of forming, but they can spread the virus at any point during the outbreak, starting from the initial tingling stage. That means no kissing from the moment you feel that familiar itch or numbness on your lip. This applies to kissing a partner, but also to kissing children, babies, or anyone else on the face.
Oral sex during an active cold sore is one of the most common ways HSV-1 spreads to the genitals. Johns Hopkins Medicine is direct on this point: abstain from performing oral sex if you have blisters or open sores around your mouth. HSV-1 genital infections are increasingly common, and this is thought to be a major reason why. The virus can even transmit when symptoms are mild or when sores are just beginning to form.
Don’t Share Personal Items
While the virus doesn’t survive long on surfaces, it can persist briefly on hard objects that come into direct contact with your mouth. During an active outbreak, don’t share:
- Cups, straws, and utensils that touch your lips
- Lip balm, lipstick, or any cosmetics applied near the sore
- Toothbrushes
- Towels and washcloths used on your face
- Razors
Soft, porous items like towels are lower risk than hard objects like drinking glasses, but it’s safest to keep all of these to yourself until the sore is fully healed. Once the outbreak is over, replace your toothbrush. The bristles can harbor the virus, and reusing an old one could potentially contribute to a new outbreak.
Don’t Pop or Pick at the Blister
Cold sore blisters are filled with fluid that contains a high concentration of the virus. Popping them doesn’t speed healing. It does the opposite: it exposes raw skin underneath, increases the risk of bacterial infection on top of the viral one, and spreads viral fluid to surrounding skin. The scab that forms over a cold sore is part of the healing process. It protects the new skin growing beneath it. If the scab cracks on its own, gently clean the area and let it re-form. Picking at it repeatedly can extend healing well beyond the typical two-week timeline and increase the chance of scarring.
Don’t Skip Sun Protection
Ultraviolet light is one of the most reliable triggers for cold sore recurrence. UV-B radiation can reactivate dormant herpes simplex virus, and outbreaks tend to develop right at the site of sun exposure. If you’re prone to cold sores, unprotected sun on your lips is essentially an invitation for the next one.
Use a lip balm with SPF 30 or higher every day, not just during an active sore. This is especially important before skiing, hiking, going to the beach, or spending extended time outdoors. Reapply after eating or drinking. During an active outbreak, sun exposure can also worsen inflammation and slow healing, so keeping the area protected serves double duty.
Don’t Ignore Early Symptoms
Most people who get recurring cold sores recognize the warning signs: a tingling, itching, or slight numbness on or near the lip before anything is visible. This prodromal stage is your best window for starting antiviral treatment. Antiviral creams or pills work significantly better when applied at the first tingle rather than after blisters have already formed. Waiting until the sore is fully developed means you’ve missed the period when treatment can shorten the outbreak most effectively.
The prodromal stage is also when you should start taking precautions around others. The sore is already contagious before you can see it.
Don’t Load Up on High-Arginine Foods
The herpes virus needs an amino acid called arginine to replicate. Foods particularly high in arginine include peanuts, other tree nuts, whole grains, and certain legumes. While the science isn’t definitive, the theory is straightforward: arginine fuels viral replication, and another amino acid called lysine competes with it. During an active outbreak, it’s reasonable to cut back on heavy nut and seed consumption and lean toward lysine-rich foods like chicken, beef, fish (especially cod and sardines), cheese, and soybeans.
This isn’t a cure, and eating a handful of peanuts won’t guarantee a flare-up. But if you notice a pattern between certain foods and your outbreaks, shifting the balance toward lysine-rich protein sources is a low-risk adjustment worth trying.
Don’t Use Harsh Products on the Sore
Applying rubbing alcohol, hydrogen peroxide, or other harsh disinfectants directly to a cold sore can irritate the already damaged skin and slow healing. The same goes for heavy makeup applied directly over the blister. Cosmetics can introduce bacteria, and the friction of application can break the scab. If you need to cover a cold sore for cosmetic reasons, use a hydrocolloid cold sore patch, which protects the area while keeping it moist for faster healing. Avoid exfoliating products, strong acne treatments, or any abrasive skincare near the sore.
Don’t Assume You’re Safe After the Blister Pops
A common mistake is thinking the sore is no longer contagious once the blister stage passes. Cold sores remain contagious through the entire scabbing phase until the scab falls off naturally and the skin underneath looks normal. That final step, the scab detaching on its own to reveal healthy pink skin, is your signal that the outbreak is truly over. The full cycle from first tingle to complete healing typically takes 10 to 14 days. Until you reach that endpoint, continue all precautions: no sharing items, no kissing, no touching without washing your hands afterward.