Doxycycline has been shown to be beneficial in Parkinson’s disease, multiple sclerosis, relapsing multiple sclerosis, heart disease and prevention of heart attacks, COPD, asthma, lupus, Grave’s orbitopathy, glaucoma, and rosacea, in humans and in animal studies, alone or in combination with other drugs. Anti-parasitic drugs have also been shown to be beneficial in lupus, rosacea, and rheumatoid arthritis. The fact doxycycline and anti-parasitic drugs improve chronic diseases informs as to the potential infectious causes; and should direct diagnosis and treatment, and medical research into the infectious pathogens responsive to doxycycline and anti-parasitic drugs.