Despite gaining mainstream support the focal infection theory had it detractors.

This was called the "focal infection theory", and it led some dentists to advocate dental extraction.

All these factors have resulted in a disagreement not only about when focal infection theory fell out of favor but also the degree to which it did.

Bearing the above in mind, it is useful to now examine the resurgence of the focal infection theory of disease in its newer guises."

Meyer was skeptical of autointoxication and focal infection theories (then viewed as the cutting edge concept of scientific medicine)as biological causes of behavioral abnormalities.

Frank Billings formally introduced the focal infection theory to American physicians in 1912 with his lectures at Stanford University Medical School being published in 1916.

In 1940, H.A. Reimann and W.P. Havens, published what was perhaps "the most influential critique of the focal infection theory", showing that it was completely unproven.

Hasselgren observed, "[t]he focal infection theory, supported by many including Dr. Price, has been attacked, debated, accepted, criticized, agreed upon, etc. but it has not been covered up."

Price initially did dental research on the relationship between endodontic therapy and pulpless teeth and broader systemic disease, known as focal infection theory, a theory which resulted in many extractions of tonsils and teeth.

In 1989 a respected study showed a significant correlation between poor dental health and myocardial infarction, which was followed by other studies showing similar results, prompting the dental community to do a cautious reevaluation of focal infection theory.

Focal infection theory as a primary cause of systemic disease rapidly became accepted by mainstream dentistry and medicine after World War I, largely on the basis of what later turned out to be fundamentally flawed studies providing evidence to support the theory.

When the presentation was printed in the 1920 Journal of the National Dental Association a dentist named Titeston praised Kells for his stance and went further saying the tooth extraction craze resulting from focal infection theory qualified as a fad.

Furthermore the mechanism of focal infection theory survived in general medicine with regards to specific diseases such as tuberculosis, gonorrhea, syphilis, pneumonia, typhoid fever, and mumps as well as conditions such as idiopathic scrotal gangrene and angioneurotic edema.

Focal infection theory (FIT) is the idea that a local infection affecting a small area of the body can lead to subsequent infections or symptoms in other parts of the body due either to the spread of the infectious agent itself or toxins produced from it.

In a 2000 issue of the Journal of the California Dental Association Pallasch stated "The focal infection theory was (is) elegant in its simplicity and offered quick and easy (as well as lucrative) solutions to a myriad of problems for which medicine had no answers.

Robert T Morris in a December 13, 1918, address to the Eastern Medical Society stated focal infection theory was already falling into disrepute in certain fields due to the other-enthusiasm of some of its advocates and stated that more evidence was needed before the medical profession continued taking active interest in the matter.