prophylaxis

noun

pro·​phy·​lax·​is ˌprō-fə-ˈlak-səs 

 also  ˌprä-

plural prophylaxes ˌprō-fə-ˈlak-ˌsēz 

 also  ˌprä-

: measures designed to preserve health (as of an individual or of society) and prevent the spread of disease

Did you know?

In Greek, phylax means "guard", so prophylactic measures guard against disease by taking action ahead of time. Thus, for example, before the polio vaccine became available, prophylaxis against polio included avoiding crowds and public swimming pools. These days a well-known kind of prophylactic is used to prevent sexually transmitted diseases; but prophylactic measures only work when people use them.

Examples of prophylaxis in a Sentence

Recent Examples on the Web

After a rabies exposure, people should seek immediate preventative medical care, known as post-exposure prophylaxis, which involves thoroughly cleaning the wound and receiving a rabies vaccination. —Shiv Sudhakar, FOXNews.com, 5 Sep. 2025

Prevention tools like contraception and pre-exposure prophylaxis (PrEP) helped protect women’s health. —Jennifer Lotito, Forbes.com, 27 Aug. 2025

People who have been exposed are advised to get post-exposure prophylaxis, which includes a dose of human rabies immune globulin (HRIG) and a four-dose series of rabies vaccine. —Beth Mole, ArsTechnica, 13 Aug. 2025

In July, 2012, the Food and Drug Administration approved Truvada, a pre-exposure prophylaxis effective at preventing H.I.V. infection colloquially known as PrEP. —Emily Witt, New Yorker, 24 July 2025

Word History

Etymology

borrowed from New Latin, from Greek prophylak-, stem of prophylássein "to keep guard before a place, be on guard, (middle voice) to be on one's guard against, take precautions against" (from pro- pro- entry 1 + phylássein "to keep watch on, guard, preserve," derivative of phylak-, phýlax "guard, guardian, protector") + -sis -sis — more at phylactery

First Known Use

1683, in the meaning defined above

Phrases Containing prophylaxis

• post-exposure prophylaxis
• preexposure prophylaxis

Rhymes for prophylaxis

• chemotaxis
• epistaxis
• anaphylaxis
• axis
• praxis
• taxus
• chemoprophylaxis

Medical Definition

prophylaxis

noun

pro·​phy·​lax·​is -ˈlak-səs 

plural prophylaxes -ˈlak-ˌsēz 

: measures designed to preserve health and prevent the spread of disease : protective or preventive treatment

prophylaxis against viral diseases

a paste containing fluorine for dental prophylaxis