The causes of toxic shock syndrome (TSS) are not fully understood, although several risk factors have been identified.

Bacteria

The bacteria involved in TSS – Staphylococcus aureus and Streptococcus pyogenes – can be found on the skin and in the nose or throat of healthy individuals, where they usually cause no serious problems.

Most people have toxin-fighting proteins known as antibodies, which can protect the body against these toxins. However, for reasons that are unknown, a small percentage of people do not develop these specific antibodies.

What is known is that the bacteria can enter the body through a wound, burn, the throat or the vagina. They release toxins into the bloodstream. These toxins cause inflammation, interfering with the processes that regulate blood pressure and causing it to drop to a dangerously low level. This results in multiple organ failure, usually affecting the kidney. The bacteria also attack tissues, including the skin, muscles and organs.

Risk factors

The following factors are thought to increase the risk of toxic shock syndrome:

• a woman being on her period – especially if she leaves a tampon in for a long time (see below)
• using female barrier contraceptives, such as a contraceptive diaphragm
• developing a wound infection after having surgery
• having a staphylococcal infection or streptococcal infection
• using nasal packing to treat a nosebleed 
• having a baby
• having a skin wound such as a cut, burn or recent chickenpox

Tampons

The role of tampons in TSS remains unexplained. One theory is that if a tampon is left in your vagina for some time, as is often the case with the more absorbent types of tampons, it can become a breeding ground for the bacteria.

Another theory is that the fibres of the tampon may scratch your vagina, allowing the bacteria or the toxins to enter the blood.

No evidence has been found to support either theory.