Hi Had very bad flu and took GeloMyrtol and...

what to do in your case mouth blister ?
1. have plenty of warm fluids 
2. drink containing vitamin C drinks or food 
3. sesame oil and sesame syrup
4. use mouth washs that contain chlorhexidine 
5. gels or designs medications for mouth blister that contain special herb or vitamin for your case such as vitamin B2 
6. if you condition presisit , consult an dental doctor to do the needed medical examination and determine the treatment pathway
what are the causes of mouth blister ?
the cause is still unclear , but its most likely to have mouth blister in those condition :
1. if you have history of mouth ulcers or family history 
2. got cold , or wearing less needed cloths according to weather temprature 
3. in presisitant cases or severe symptoms , viral infection may be the cause