Toxic shock syndrome (TSS) is a rare, but severe, type of blood poisoning that affects about 40 people a year in the world half of whom are women using tampons. Therefore your risk is very, very small.The condition can be fatal if not treated soon enough, but this is rare. It’s caused by bacteria that usually live harmlessly on your skin and in your vagina, nose, groin or armpit, producing toxins that overwhelm your immune system. Most women are not at risk because they produce antibodies against the toxins that cast TSS. Its not known why tampons can increase the risk of TSS, but to reduce the tiny risk, always use the lowest-absorbency tampon for your blood flow, change tampons at least every four to eight hours and follow the manufacturer’s instructions carefully.