Cold sores are small clusters of blisters on or around the lip, caused by the herpes simplex virus. The virus stays in the body for life, but episodes get shorter when treatment starts early, and for most people they become less frequent over the years. Aphthous ulcers are painful non-contagious sores inside the mouth.
The same eight facts on every condition comparison.
Blister cluster Small blisters on the lip edge.
Crusting Yellow crust as it heals.
Near the nose Can appear around the nostrils.
Canker Sores A small shallow ulcer has a red rim and a lighter center.
Herpes simplex virus remains in sensory nerves after the initial infection. Reactivation brings the virus back to nearby skin, where local viral activity can produce grouped blisters.
Local inflammation damages the mouth's surface lining and forms an ulcer. The exact cause is often uncertain, and several triggers may contribute.
Cold Sores. The first infection often occurs early in life; recurrent episodes can occur at any age afterward.
Canker Sores. Often begins in childhood or adolescence and may recur.
Cold sores are caused by the herpes simplex virus. After the first infection, the virus stays in nerves and can reactivate.
A local inflammatory ulcer develops; the cause is often uncertain.
Evidence labels come from each condition’s own treatment list.
The only over-the-counter cream shown to shorten an episode, and only by about half a day. It has to go on at the first tingle and be reapplied five times a day. It is a reasonable thing to keep in a bag, but antiviral tablets started at the same moment do considerably more.
Strong sun on the lips is one of the most reliable triggers there is, so for anyone whose episodes follow skiing, a beach holiday or long days outdoors, a daily SPF lip balm is genuine prevention rather than lip care. Use it every day rather than only when an episode is due, and keep using it while the mark left behind fades, since sun makes that darker and slower.
A thin gel patch worn over the sore. It keeps the area moist so the crust splits less, it stops fingers reaching the sore, and it contains the fluid that spreads the virus. It does not shorten the episode itself, and it is easier to use once the blisters have opened than at the tingle stage.
A popular supplement for preventing episodes, but the studies behind it are small, old and inconsistent. It is not dangerous and some people are convinced by it. It is not a substitute for an antiviral, and it is not something to rely on if your episodes are frequent.
Plain ointment dabbed over the crust keeps it soft so it does not split each time you talk or eat, which hurts less and leaves less of a mark. Drying the sore out does the opposite of what people expect. Apply it with a clean fingertip or a cotton bud and wash your hands afterwards - it does nothing to the virus itself.
Penciclovir cream. A prescription antiviral cream applied every two hours while awake for four days. It shortens an episode by around half a day to a day, so a little more than the over-the-counter cream and a lot less than tablets. It is a reasonable option for someone who cannot take the tablets.
Acyclovir cream. The cream version of the tablet, five times a day for four days. The virus is multiplying deep in the skin cells and traveling in a nerve, so a cream only reaches part of the problem, and the benefit is measured in hours rather than days. If you can take the tablets, take the tablets.
A clinician may recommend a mouth-specific preparation for troublesome recurrent ulcers.
The usual first choice, and for a cold sore it is a single day of treatment - two large doses twelve hours apart, started at the first tingle. Taken then, it shortens the episode and can stop a blister forming at all. Started after the blister is out it does much less, which is the whole argument for keeping a course at home.
An equally effective alternative, taken as a single dose at the first tingle, which suits people who will not manage a second dose later in the day. It is used where valacyclovir does not suit or is not available. It is usually the more expensive of the two.
The oldest of the antiviral tablets and the cheapest. It works, but it has to be taken five times a day for five days, which is a lot of doses for something that lasts a week anyway. The dose is lowered if your kidneys are not working well.
A low dose of the same antiviral taken every day, rather than only during an episode, for people getting roughly six or more a year. It reduces how often they happen substantially and lowers the amount of virus shed in between. The effect stops when the tablets stop, and doctors usually review it after six to twelve months.
Most episodes run a week to ten days. People settle into a rhythm - one or two a year, or several, and some have one episode and never another. Frequency drops with age.
Most minor canker sores heal within 1–2 weeks without scarring, but episodes can recur. A persistent, unusually large or repeatedly troublesome ulcer needs assessment.
Herpes can occasionally spread to the eye or extensively through eczema-affected skin. Eye pain, widespread painful blisters, or exposure of a newborn requires prompt medical advice.
Frequent severe ulcers can accompany nutritional deficiency or inflammatory disease.
Seek care for severe, frequent or persistent episodes. Eye pain or redness, widespread blisters with eczema, or illness in a newborn needs urgent assessment.
Have an ulcer lasting over two to three weeks, frequent severe episodes or ulcers with other symptoms assessed.
Almost certainly in childhood, from ordinary contact with someone who carried the virus - a kiss, a shared cup or spoon. Most people have no memory of it, because the first infection often causes nothing. It is not about hygiene or anything you did.
Most easily passed on from when blisters appear until the sore has fully crusted - roughly the first four to five days. Small amounts are shed when nothing is visible. Precautions matter most around newborns, eczema and anyone immune-suppressed.
Because the virus lives in one nerve, which supplies one small patch of skin. When it reactivates it travels down to that patch. Some people have two or three usual spots.
The virus stays in the body permanently, so there is no cure. But episodes usually become less frequent over the years, and daily suppressive treatment can reduce them a great deal. Plenty of people effectively stop having them.
Not while you have an active sore. Herpes simplex is dangerous in newborns in a way it is not in older children or adults. Do not kiss the baby, wash your hands before handling them, and cover the sore. If a newborn develops blisters or a fever, or becomes unusually sleepy or floppy, that is an emergency.
Less well. Antiviral tablets stop the virus multiplying, and by the time blisters are out most of that has happened. Still worth taking for a severe episode, but the benefit is in the first 24 hours.
Aphthous ulcers are painful non-contagious sores inside the mouth.
Avoid irritating foods and traumatic brushing; use a gentle oral-care routine.
Have an ulcer lasting over two to three weeks, frequent severe episodes or ulcers with other symptoms assessed.
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