nonpathogen
A carcinogen is an agent that causes cancer.
The medical term for an agent that causes cancer is "carcinogen." Carcinogens can be chemicals, radiation, or viruses that are known to promote the development of cancer in living tissues.
pathogenAn agent of infection is a pathogen.
A cytotoxin is an agent that kills cells
In medical terms, an agent usually refers to a medication. For instance, an antihypertensive agent reduces blood pressure.
A teratogen is an agent that causes birth defects.
An antimotility agent controls loose stools.
An antineoplastic agent is one that works against tumors. A tumor is also known in medical terms as a neoplasm.
Antagonist is a process or agent that works against another.
The word you're searching for is "etiology", as in; "The patient presented complaining of severe lower back pain, etiology unknown."Etiology means cause of an illness.
bronchodilators
An agent used to increase the effectiveness of a medication is a "potentiator".An agent used to increase the effectiveness of a medication is a "potentiator".