Thank you for the query.
The history given suggests of formation of ulcers which in early stage present this way ,initially they wont be painful but later will develop pain . This is because of the vitamin deficiency
or stress . As you said ,the climate again may be a factor leading to xerostomia
, numbness of the lip ,causing sores in the mouth and dryness of lips leading to swelling because of the it.
This can be treated by using chlorhexidine
mouth wash and application of dentogel on the sores, multivitamin
intake, take more water and proper food .
If still the swelling and numbness persists see your dentist
Hope this information helps you.