The author found that the onset of hypertension or hypotension is relatively often associated with infections or development of so-called "sneezing due to allergy to pollen or dust," with or without headache, or due to trauma to the occipital area of the head. Using the "Bi-Digital O-ring Test," it was possible to demonstrate that, among bacterial and viral infections, the most common cause of infection associated with the appearance of hypertension is chlamydia, herpes simplex virus, cytomegalovirus, or Epstein-Barr virus. Particularly chlamydia and/or herpes simplex virus, with or without coexistence of other microbes, is usually present at the heart representation area of the medulla oblongata, especially at the left ventricular representation area, often accompanied by upper respiratory infection, cephalic, cervical or facial pain, with or without coexisting genito-urinary infection. The left ventricular representation area of the medulla oblongata is usually located at the right side. In most hypertensive patients, the left ventricular representation area of the medulla oblongata is enlarged up to 3 or 4 times normal size. Sufficient antibiotic treatment of chlamydia with erythromycin sometimes eliminated severe hypertension which appeared after chlamydia infection. In the presence of viral infections, such as herpes simplex, which is also causing severe pain in the head or neck, oral administration of acyclovir, erythromycin, or EPA (Eicosa Pentaenoic acid)-DHA (docosa hexaenoic acid) Omega 3 fish oil often reduced associated intractable pain and hypertension toward the normal level. Thus, the author is proposing new possible mechanisms as among the causes of so-called essential hypertension as a result of microbial infection or trauma of the cardiovascular representation area, particularly that of the left ventricular representation area at the right side of the medulla oblongata.