I'm currently in training for a long distance charity walk (100km) however I've started to notice a reoccuring issue that has come about on my longer walks (30km+) that oddly I don't tend to get when cycling long distances and that is in the days after a longer walk my lips get really dry and chapped. At first I thought it might be a hydration issue but I've really dialled that in and on my most recent hike where I covered 75km in 12 1/2 hours I was able to keep really well hydrated with of places to refill my hydration bladder and made sure I was regularly topping up with electrolytes. I also made sure to keep applying the vaseline I was carrying for other chafing related issues regularly but still in the days following my lips are really painful.
The only thing I can think of is that I tend to do these longer distances on fairer days and it could be something to do with sun exposure but I'm not sure because I didn't burn anywhere else? I must admit that I've really only been walking properly like this for the last year or 2 and the last time I was doing distances like these was when I was a teenager so I still have a fair amount to learn and hopefully someone might have a few tips or tricks to pass on.