Is it true that a body temperature of 40 degrees Celsius, or 104 degrees Fahrenheit, can kill all cancer cells? No, that's not true: A fever can be a symptom of all cancers and a medical emergency during chemotherapy. Additionally, the temperature for effective hyperthermia, a treatment that involves heating the body, requires a temperature of 45 degrees Celsius, or 113 degrees Fahrenheit, to treat some advanced cancers below this skin.
The claim appeared on TikTok (archived here) by user @positive1931 on February 13, 2024. The video features a list of body temperatures and what they mean, citing a temperature of 39.6 degrees Celsius as one that kills breast cancer cells, and 40 degrees Celsius as one that kills all cancer cells (translated from Japanese to English by Lead Stories staff):
The law of body temperatures:
40°C: All cancer cells die
39.6°C: Breast cancer cells die
This is what the post looked like on TikTok at the time of writing:
(Source: TikTok screenshot taken on Thu Feb 22 16:34:55 2024 UTC)
A body temperature of 40 degrees Celsius does not effectively kill cancer cells in the body. In fact, fevers are often a common symptom of cancer (archived here), especially the types that targe the lymph nodes, blood cells, kidneys and liver (archived here). A fever is also a sign of an infection, which is often classified as a medical emergency during chemotherapy (archived here).
While there are treatment methods that involve heating the body to a high temperature, such as hyperthermia, the necessary body temperature required to effectively kill cancer cells is said to be 45 degrees Celsius (archived here).
