<s>[INST] A couple weeks ago I noticed the corners of my mouth/lips had turned white after returning from my first ever 2 week vacation in Europe. I didn t know if it could be related to either whitening toothpaste or the cankers I always get/have in my mouth, which I ve never sought medical attention for, or something else. [/INST] Dear patient Whitening at corners of mouth mostly is due to riboflavin and multivitamin deficiency.  Riboflavin is essential for mucosa and skin well being and it's deficiency leads to stomatitis and white patches. You need to consult physician and get yourself examined.  Start tab becozinc once a day for  7 days. All the best. </s>