As mentioned, many conditions, infections, medications or combination of these can cause mouth ulcers, sore throat, taste change, and pain.

When my kidney function goes down, I notice taste changes, and in some cases, it can cause mouth ulcers, sore throat, medications like Gabapentin, which I take, as well as pain Meds, can cause taste changes, throat swelling. Antibiotics too can cause taste changes, and conditions like Thrush, a fungal infection, can cause taste changes, ulcers, and pain, but this sometimes needs to be treated with Antifungals, and likewise with a viral infection, like herpes simplex virus, with an antiviral, and mucocitis can cause ulcers to become bacterial infections, and need to be treated with antibiotics. Even dehydration contributes, and has similar symptoms, so it's good he's seeing his doctor who can help, and perform any necessary tests such as blood test, culture test.

Btw, I still carry a water bottle with me everywhere I go.

Good luck


10/09 T1N2bM0 Tonsil
11/09 Taxo Cisp 5-FU, 6 Months Hosp
01/11 35 IMRT 70Gy 7 Wks
06/11 30 HBO
08/11 RND PNI
06/12 SND PNI LVI
08/12 RND Pec Flap IORT 12 Gy
10/12 25 IMRT 50Gy 6 Wks Taxo Erbitux
10/13 SND
10/13 TBO/Angiograph
10/13 RND Carotid Remove IORT 10Gy PNI
12/13 25 Protons 50Gy 6 Wks Carbo
11/14 All Teeth Extract 30 HBO
03/15 Sequestromy Buccal Flap ORN
09/16 Mandibulectomy Fib Flap Sternotomy
04/17 Regraft hypergranulation Donor Site
06/17 Heart Attack Stent
02/19 Finally Cancer Free Took 10 yrs