I recently chatted with a cousin who is a physician in Florida. He told me about a patient in their clinic system who for years had been plagued by chronic otitis externa (inflammation of the ear canal; "swimmer's ear").
Otitis externa may be acute (lasting less than six weeks) or chronic (lasting more than three months). Acute cases are typically due to bacterial infection, and chronic cases are often due to allergies and autoimmune disorders. The most common cause of Otitis externa is bacterial. Risk factors for acute cases include swimming, minor trauma from cleaning, using hearing aids and ear plugs, and other skin problems, such as psoriasis and dermatitis. People with diabetes are at risk of a severe form of malignant otitis externa. Diagnosis is based on the signs and symptoms. Culturing the ear canal may be useful in chronic or severe cases.
This patient had received multiple courses of conventional therapy (cleaning, eardrops, antibiotics etc) with no resolution of the process. Then one day he returned to clinic in total remission - asymptomatic and with a normal otoscopic exam. When he was asked what recent treatment had worked, he replied that he had taken some earwax from his "good ear" and placed it in his "bad ear." After that, the inflammation had subsided and then resolved.
This is an anecdotal case report, from a series of n=1, and as far as I know is unpublished, but it is clearly suggestive of the importance of the individual's microbioime. Of note, this event occurred many years before even the concept of the human microbiome had been understood or published. The patient figured this out on his own.