Cold sores -- painful blisters and open sores that usually develop on or around the lips -- have plagued people for centuries. In fact, according to the National Institute of Dental and Craniofacial Research, the Roman emperor Tiberius banned kissing in public ceremonies in an attempt to reduce their spread. Today, cold sores are still spread through kissing, and there is still no cure for the virus that causes them. Caffeine, a stimulant found in many foods, exerts both positive and negative effects on cold sores.
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Caffeine is a stimulant, which means that it helps people stay awake and alert, and a diuretic, which means that it promotes urination. It occurs naturally in many foods, including coffee, cola, cocoa and tea. Synthetic caffeine is added to energy drinks, some noncola soft drinks and over-the-counter medications for headaches and allergies. Pure caffeine is bitter, but otherwise tasteless.
Caffeine decreases the spread of the virus that causes cold sores, at least in test tubes. A July 1998 study published in Neuroscience Research extended that finding to animals, demonstrating that rats with cold sores who were treated with caffeine experienced less discomfort and faster healing compared to untreated rats. However, caffeine’s stimulant properties can cause insomnia, while adequate sleep is one of the lifestyle factors that influences the duration and severity of cold sores.
MedlinePlus, a patient information service sponsored by the National Institutes of Health and the National Library of Medicine, cautions that caffeine can cause side effects including increased heart rate, increased urination, nausea, vomiting, agitation, anxiety, depression, tremors and sleeplessness. Women who are pregnant should talk to their doctors before consuming caffeine because it can result in lower-birth-weight babies. People with coronary artery disease and peptic ulcers should also consult their doctors, because caffeine can make these conditions worse. People who consume caffeine regularly may become addicted. Abrupt withdrawal may produce headaches, drowsiness, irritability, nausea, vomiting and other problems.
As of January 2014, there's no definitive evidence to suggest that caffeine can cure or treat cold sores. The Neuroscience Research study suggests that caffeine may be beneficial; however, compounds that are beneficial in animals do not always work well in humans. In addition, the study used a 10 percent caffeine gel product that is not commercially available. In addition, a study published in the October 2011 issue of the "International Journal of Molecular Medicine" found that while compounds in coffee can prevent herpes virus growth, it might not be effective after the virus has infected tissue. Although many popular beverages contain caffeine, the concentration of caffeine is lower -- between 2 percent and 4 percent -- because beverages make only brief contact with the tissues of the mouth and the lips, compared to the product in the study, which was allowed to sit on the affected skin.
MedlinePlus says moderate consumption -- three or fewer servings per day -- of caffeine-containing food and beverages probably exerts no negative effects on health, especially in the context of an otherwise healthy lifestyle. For all people, especially those with cold sores, this means getting enough rest and exercise, managing stress and consuming a balanced diet emphasizing fruits, vegetables and whole grains. Though important, lifestyle changes do not replace conventional medical treatment for cold sores or any other medical problem. People who experience severe, frequent or long-lasting --longer than two weeks -- cold sores should consult their doctors.