Kissing offers many health benefits but may also transmit a small number of disease-causing bacteria and viruses. Bacteria and viruses in the saliva or blood of one person can be spread to another person by kissing. Some diseases are more easily spread than others.
Viruses that can be transmitted by kissing
Examples of illnesses caused by viruses that can be transmitted during kissing include:
Colds – also known as upper respiratory tract infections. Many different viruses can cause the common cold. Colds are thought to be spread by direct contact with the virus. You could catch the cold from airborne droplets or from direct contact with secretions (fluids and mucous) from the infected person’s nose and throat.
Glandular fever – also known as the kissing disease. Glandular fever is the common term for a viral infection called infectious mononucleosis, caused by the Epstein-Barr virus. The virus is spread through saliva and infection occurs through contact.
Herpes infection – viruses that are considered part of the herpes family include Epstein-Barr, varicella-zoster (causes chickenpox) and herpes simplex (causes cold sores). Herpes simplex virus can be spread through direct contact with the virus when kissing. Herpes is most easily spread to others when the blisters are forming or have erupted. The virus can be ‘shed’ (spread to others) from the site of blisters even when they have healed. Chickenpox is easily spread from person to person by direct contact, droplets or airborne spread.
Hepatitis B – kissing may also transmit this virus, although blood has higher levels of this virus than saliva. Infection can occur when infected blood and saliva come into direct contact with someone else’s bloodstream or mucous membranes. (Mucous membranes line various body cavities including the mouth and nose.) A person is more likely to be infected when kissing if they have open sores in or around the mouth.
Warts – warts in the mouth can be spread through kissing, especially if there are areas of recent trauma.
Bacteria that can be transmitted by kissing
Examples of bacteria that can be transmitted during kissing include:
Meningococcal disease – this is a potentially life-threatening condition which includes meningitis, inflammation of the membranes (meninges) that surround the brain and spinal cord, and septicaemia. These bacteria can be spread either through direct contact or via droplets. Studies show that, with respect to kissing, only deep kissing seems to be a risk factor.
Tooth decay – the bacteria that cause tooth decay aren’t found in the mouths of newborn babies! A baby’s mouth must be colonised with infected saliva, which can be passed by a kiss on the lips.
There are a number of things you can do to reduce the risk of passing on, or catching, an infection while kissing. You should try to:
Avoid kissing when you or the other person are sick.
Avoid kissing anyone on the lips when you, or they, have an active cold sore, warts or ulcers around the lips or in the mouth.
Maintain good oral hygiene.
Cough and sneeze into a hanky if you have a cold.
See your doctor about immunisations. Vaccines are available to prevent some infectious diseases, such as chickenpox, hepatitis B and group C meningococcal infection.