Science Questions

Why are cold sores so painful?

Sun, 14th Dec 2008

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Lyell Wallince asked:

Why are cold sores so painful?


Chris - Cold sores are the herpes virus - this is herpes simplex.  There are two types of herpes simplex: type 1 and type 2.  Cold sores traditionally are caused by type 1 herpes.  This is a virus that gets into your body, usually by the age of 3 most of us have picked it up by kissing a parent.

In the first manifestation it goes into cells in the mouth and throat and infects those cells to amplify the virus many times over and increasing the infectious dose.  The first presentation is you get a sore throat and high temperature; your glands come up around your throat.  It then appears to go away for a long time, some people never see it again.

What actually has happened when you had a sore throat was the virus was also infecting sensory nerve endings that supply your mouth and throat.  These nerve endings then transmit the virus back to the spinal cord or to what’s called the dorsal ganglion which is where the cell body for those nerves lives; adjacent to your spinal cord.  In the case of the head and neck it goes up to the trigeminal ganglion which is underneath your brain.  This is where the virus hangs out just as a small circular piece of DNA for the rest of your life.  If you go to the post mortem room and you study people you’ve died you can find evidence of the virus living in 80% of the population’s nervous system.

Periodically and in response to poorly defined stimuli (these can include menstruation, they can include sunburn and tissue trauma – if you get a cigarette burn this can sometimes make it happen) some signal goes back up the nerve, says to the virus, “you’re threatened, you need to come out.”  It reactivates and the DNA turns on again, makes fresh virus particles inside the cell.  They come back down the nerve cell to a patch of skin that nerve cells supplies, the virus comes out of the nerve, onto the skin, raising the skin cells producing an infectious lesion.  That’s a cold sore and the point of this is the virus uses the cold sore to infect another person - when you kiss someone you’re infectious.  That’s how the virus gets around but the rest of it is hiding inside your nervous system.

When it reactivates in that way it can damage the nerve it’s in and those nerves very often are pain nerve fibres.  They get stimulated by the activation of the virus and that is excruciatingly painful and it can persist for a very long time.


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Lyle Rawlins  asked the Naked Scientists:
Hi guys,

I've now listened to all the Naked Scientist podcasts and am enjoying the "Ask the Naked Scientist" podcasts.

I am curious to know why a cold sore can be so intensely painful. The worst pain I have had in my life was from a cold sore, it would throb clear down to the bottoms of my feet. How is it that a relatively small outbreak on your lip can literally shoot pain from head to toe?

After a couple of days of this I had tried nearly every remedy to make it go away and nothing worked. My last, and successful, remedy was to apply liquid bleach directly to the sore. Sure it hurt so bad I nearly wet my pants, but within hours the sore had dried up and the pain was gone.

I still get the occasional outbreak but now at the first tingle apply a dab of bleach and start taking lysine to quickly tame the beast.

Keep up the good work!

Lyle Rawlins

Corona, California

What do you think? lrawlins, Thu, 16th Oct 2008

Cold sores are a result of an attack by herpes simplex a virus that is similar to the one that causes chicken pox.  it is a virus that attacks nerves so that is one of the reasons it causes peculiar sensations.

The virus travels down nerves and can be latent for years in the facial nerves and usually emerges to create havoc after the attack of another virus over exposure to sunlight reduced immunity or general poor health and can in rare cases be extremely nasty and cause brain damage.

You catch the virus by physical contact with someone who is infected with the virus.

I would not reccommend treating cold sores with bleach or annoy other violent antiseptic.  It could do much more harm than good

There is an excellent antiviral drug Acyclovir which applied to the spot in a cream should be used to treat cold sores at the first tingle.  This will not only stop the attack bu reduce the chances of further attacks in the future This is now available over the counter in the UK.  A trade name for Acyclovir is Zovirax.

I have suffered from cold sores ever since I was a child but now get them very rarely thanks to the use of this drug.  Unlike you I never found cold sores very painful, a bit tingly when they start and stingy when they have developed into an open wound. however I believe that a more extensive version of the similar virus known as "Shingles" or Herpes zoster which can appear elsewhere on the body (including the genital area) can be very.

It is wise to take great care with personal hygiene when one has a cold sore and definitely never kiss any other person while it is active Soul Surfer, Thu, 30th Oct 2008

Cold sores are painful only because they stay for longer period of time and the virus which causes this infection can not be eliminated completely with help of any OTC treatments. Most cold sore infections can be recurrent and can produce severe skin itchiness, rashes, swollen glands as well as genital herpes. So it is essential to take care of the infection as soon as possible. There are several natural cold sore remedies that are easy to make at home and do not cost fortunes. You can find the best natural cold sore remedies at the following resource.

<spam-be-gone! spell used. - Mod> Jenny Jackman, Fri, 26th Aug 2011

I have tried just about every product/ice/natural cure/etc.  Best thing I have found by far is viradux-coldsore.  You just use it like a chapstick 4x per day and no more gross cold sores.  I think it's fairly new.  Hope this helps! heliski55, Sat, 9th Mar 2013

Zovirax is very overpriced when compared to "own brand" acyclovir, all the major supermarkets sell one which is often a quarter of the price of Zovirax, and works just as well, I can assure you. Also, I find that any Acyclovir cream has a relatively short shelf life, 6months tops - it isn't apparent by looking at it, it simply isn't as effective. If you don't suffer regularly, buy a new cream each time for maximum effect (IMO)

SOME coldsore sufferers can transmit the virus, for example, via kissing, even when the coldsore isn't 'active' or apparent to them. It depends on which specific herpes someone is carrying to determine whether this is the case. You can also carry herpes but never suffer the facial/skin blemishes. Rystok, Mon, 11th Mar 2013

Last time I went to the doc I was just starting to show the blisters, and along with the Acyclovir he gave a short course of ARV's as well. Not had them in the 6 months since, so possibly it does help. Was not the reason I went there, but nice to have the 2 for 1 treatment, I actually went there to get the repeat script for some hayfever meds. SeanB, Tue, 12th Mar 2013

Cold sores are painful because they are deep below the first layers of the skin causing inflammation and nerve damage. The infection causes white blood cells to attack the source of the infection, leading to further complications. To reduce the pain, you can get numbing spray or use natural home remedies, like garlic or aloe vera. I got that info from this blog article here ( in case you want to check out some other natural remedies. Cheers! davinNoMo, Fri, 26th Jun 2015

The bad news is that the virus is now in your peripheral nerve root and hiding there like the terrorists in Somalia. At some random time in the future, they will perpetrate another outrage upon the person of your lip.

That is why Joe Bob Briggs - the drive-in movie critic - says, "Never go home with a girl who says the sore on her lip comes from playing the flute."

The good news is that you live in California and the black-hearted, racist  dogs of the GOP have just today been beaten back to their tents and so no longer threaten Obamacare -- for now. They are political herpes in that regard.

Therefore, if you are covered by Obamacare's affordable health insurance, you can see the doctor and still pay the rent as soon as you feel another one of those bad old sores coming on. In effect you can get a drone strike on the herpes terrorists before they can attack. Pecos_Bill, Fri, 26th Jun 2015

I caught genital herpes from my ex boyfriend who never had any symptoms. I have had it for 1 year and 4 months now,and it has affected my life. I have told my husband who I trusted about it and I have never had a bad reaction, it has affected my new relationship with my husband. People think herpes is really a minor skin irritation herpes has a long term effects on health. The stigma attached to this virus by ignorant people is ridiculous. Most people have herpes in one form or another. I would like to advise people on how i get rid of my herpes.i was reading a comment on the internet,and i saw a testimony posted by a woman from island that she got rid of her herpes with the help of doctor Lusanda. so i was so happy when i saw that post,that his herbal medication is is genuiue .i quickly emailed him and within couple hours he responded to my email.i explain things to him he told me not to worry and within days after contacting him i received the herb via DHL.i followed the prescription of the herb.after 16 days of usage i found out that my herpes was no more my doctor was also suprise with the change, he also called 2 other doctors to conduct seperate test on me and they both came out with same result NEGATIVE,when some of my friends who had herpes saw me they were surprise and i also introduced them Dr Lusanda and they have been since cured from herpes,kindly contact Dr Lusanda via this email drlusandaherbal(AT)gmail(DOT)com or website on www(dot)drlusandaherbal(dot)weebly(dot)com Shanaye, Tue, 30th Aug 2016

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