Cold sores: why timing matters more than the medicine

Starting antiviral treatment at the first tingle changes the outcome more than which antiviral you take. Here's what that means in practice.

The window is the whole game

Most people know the feeling that comes before a cold sore appears: tingling, itching, or tightness on the lip, usually 12 to 24 hours ahead of anything visible. That period, the prodrome, is when antiviral treatment does the most good. Started then, a course can shorten the outbreak by a day or two and sometimes stop the blister from forming at all.

Started after the blister has crusted, the same medication does very little. This is why we ask so specifically about when your symptoms began, and why a visit at the first tingle is worth more than a visit three days in.

Which medication matters less than you'd think

Acyclovir, valacyclovir, and famciclovir all work through the same mechanism and perform similarly in head-to-head studies. The differences are practical: dosing frequency, cost, and kidney considerations. Your provider picks based on your history, not on one being clinically superior.

If you get them often

Recurrent outbreaks, six or more a year, are the situation where suppressive therapy, a lower daily dose taken continuously, is worth discussing. It's also worth identifying your triggers: sunlight is a common one, and daily lip balm with SPF prevents more outbreaks for some people than any prescription does.

When it isn't a cold sore

• •Sores inside the mouth, on the gums or tongue, are more often canker sores, which are a different problem with different treatment
• •A first-ever outbreak with fever and swollen glands can be more extensive and deserves a closer look
• •Sores that don't heal within two weeks, or keep returning to the exact same non-lip spot, should be examined in person