I went on a business trip in Lagos, Nigeria for 2 weeks with colleagues. After coming back to Paris, France, 3 of us are having canker sores. Mine appeared about 2 days after coming back, I don't know for the other

As there seem to be no clear consensus on what exactly causes them, I am looking on explanations on what factors could have helped their apparition, and how we could possibly mitigate them, as we are going to travel somewhat regularly to Nigeria.

Here are a few points I think could be leads on the reasons of canker sores:

  • Weather is far colder (5-10°C v about 30°C) and drier in Paris than in Lagos.
  • Lagos feels a lot more polluted than Paris -even though it can only be an impression linked with the colder weather - and walking near a big street felt like it was hard to inspire among all the exhaust gas.
  • We ate more spicy food then in Lagos than now in Paris, however it would seem as a reason on having canker sores there, rather than having them when coming back.

EDIT : to clarify, I am not asking for a treatment, even preventive (though I'd be interested to hear about it), but rather on what possible causes (environmental, food) could have caused canker sores, and possibly ways to mitigate them. As there are questions clearly asking if they need to use a specific medical treatment or not, I don't feel like my question is off-topic, at least not on the basis on asking for health advice.

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    Canker sores may be caused by spicy food, don't have to appear immedately, but will then usually heal on their own. They may also be caused by bacteria in something you ate in Nigera and need treatment. As with all acute medical issues, I would strongly suggest that you seek professional care instead of relying on suggestions from strangers on the internet. – Tor-Einar Jarnbjo Nov 22 '18 at 17:31
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    Thank you for your comment @Tor-EinarJarnbjo . I have visited a doctor who told me to just let them heal, while being unable to explain the possible causes to me. I think however that there are people on this website who might have experience or heard about the same thing and found ways to avoid it – LoicM Nov 22 '18 at 17:52
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    I'm voting to close this question as off-topic because it is a request for health advice, which needs to be addressed to a doctor, not random people on the internet. – David Richerby Nov 22 '18 at 18:12
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    OP is not asking for treatment (which he's already sought, and been told that he should just let it be). He's asking how in future to reduce the chance of it happening. We've answered similar questions in the past, so I've voted to reopen. – MJeffryes Nov 22 '18 at 22:30
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    Also, I think it's pretty impolite to have voted down a perfectly reasonable and well written question. The down vote button is labelled "This question does not show any research effort; it is unclear or not useful", and I don't think that remotely applies to this question. – MJeffryes Nov 22 '18 at 22:31

I have always heard that mouth ulcers, (you call them canker sores,) come from a lack of vitamin C.
When I get them I do increase my fruit intake or, when that is not an option, take vitamin tablets.

It works for me.

Of course, all information in the comments on the question may hold the truth and a change in toothpaste or water may be the cause. Or spicy food.

So bring your usual brand of toothpaste, get yourself used to the same level of spice in your food before you travel, keep avoiding tap water and so on.

As with many sore spots in your mouth, rinsing with a strong alcoholic drink (40% like wiskey or rhum) might kill the pain. It is a painful method. (No rule about spitting out the drink.)

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