<s>[INST] My 21 year old has numerous canker sores in his mouth that arose 5 days ago (he's never had them before). He now also has a pounding headache.  Other than oral gel to ease the mouth pain, he has tried mouthwash and has swished with hydrogen peroxide  (not at my advice) and the pain is tremendous.are the headache and mouth sores related? or should he just treat them individually?  Advil is not relieving the headache at all (he is away at college and asking for advice.) [/INST] Hello and Welcome to ‘Ask A Doctor’ service.I have reviewed your query and here is my advice.Canker sores in the mouth can be due to a number of causes like nutritional deficiency, stress, eating more spicy and acidic foods or allergic reaction. In case if it is associated with other symptoms too then it can be due to viral infection causing cold sores. If the symptoms are too severe then better consult an oral physician and get evaluated. A clinical examination and if needed an oral swab culture test can help in diagnosis. For now to reduce pain he can continue applying numbing gels and also can gargle with a specialized mouthwash like magic mouthwash. Sucking ice or cool water rinses can help. Take Vitamin B complex daily. Take the soft diet and drink plenty of water. Hope I have answered your query. Let me know if I can assist you further.Regards, Dr. Honey Arora </s>