Can you get cancer from kissing someone who has cancer, specifically, are there any circumstances under which cancer cells could be transmitted through saliva or other close contact like kissing, and potentially establish themselves in the new host? Are there any specific cancers or treatments that might increase the risk of transmission, and what is the scientific understanding of how the immune system would react to foreign cancer cells introduced in this way? Are there documented cases of this type of cancer transmission occurring in humans through kissing?

Answer

No, you cannot get cancer from kissing someone who has cancer. Cancer is not a contagious disease. It is caused by genetic mutations within a person’s own cells.

However, there are a few very rare exceptions:

• Infectious agents that can cause cancer: Some viruses and bacteria can increase the risk of developing certain cancers. While kissing can transmit these infectious agents, it is not directly transmitting cancer. Examples include:
  • Epstein-Barr Virus (EBV): Transmitted through saliva, EBV is associated with an increased risk of nasopharyngeal cancer, Burkitt’s lymphoma, and Hodgkin’s lymphoma. Kissing is a common way to transmit EBV (hence the term "kissing disease" for mononucleosis, which EBV causes). However, most people infected with EBV do not develop cancer.
  • Human Papillomavirus (HPV): Some types of HPV are associated with oropharyngeal cancer (cancer of the back of the throat, including the base of the tongue and tonsils). HPV can be transmitted through skin-to-skin contact, including kissing, especially deep kissing or oral sex. However, most HPV infections clear on their own without causing cancer, and vaccines are available to protect against cancer-causing HPV types.
• Organ transplant recipients: In extremely rare cases, cancer has been transmitted through organ transplantation. If an organ donor unknowingly has cancer, the recipient may develop cancer from the transplanted organ. This is not related to kissing.

In summary, while kissing can transmit infectious agents like EBV and HPV that are associated with an increased risk of certain cancers, it does not directly transmit cancer cells. The risk of developing cancer from these infectious agents through kissing is relatively low, and in the case of HPV, preventable through vaccination.