Is stepping on a rusty nail really enough to cause tetanus?

Nails are essential for any building project, yet their danger is so significant that it's surprising they don't require a permit to purchase. The risk of accidentally hammering your thumb instead of the nail is high. Using a nail gun doesn't eliminate the hazard; in fact, a simple online search reveals chilling accounts of nail gun injuries. Even when you're safely in your car, a nail can still cause issues, such as a flat tire. But for many, the most perilous nail of all is the infamous rusty nail. It's widely believed that stepping on one can result in tetanus.

What is Tetanus?

Tetanus infection occurs when a certain type of bacteria enters the body, typically through puncture wounds. Once inside, the bacteria release toxins that impact the nervous system, causing muscle stiffness and spasms. Tetanus is often called lockjaw because one of its symptoms involves severe muscle contractions around the jaw, leaving it stiff and immobile.

Muscle spasms can spread throughout the body, sometimes becoming so severe that they may even lead to fractures. These spasms can also cause difficulty with swallowing or breathing. Additional symptoms include drooling, irritability, fever, and excessive sweating. These symptoms typically begin around a week after infection, though they may appear in just a few days. This is why it's crucial to seek immediate medical attention. Without timely treatment, one out of four people die from tetanus.

The tetanus vaccine is routinely given to infants, but its protection may fade over time. To maintain immunity, adults are advised to receive a tetanus booster shot every 10 years. Many people stop getting these boosters as they age, which is why older adults account for 70 percent of all reported tetanus cases. But does a rusty nail really cause tetanus? If so, why? And if not, what are the actual causes of tetanus?

What Causes Tetanus?

The old wives' tale holds some truth — stepping on a rusty nail can indeed lead to tetanus. But it’s not just rusty nails; even a clean nail, a sewing needle, or a scratch from an animal can transmit the bacteria that causes tetanus. The bacteria, Clostridium tetani, is commonly found in soil, dust, and animal feces. Gardeners and agricultural workers are particularly vulnerable to exposure, as this bacteria is often present in soil and manure. In fact, some farmers may even carry it on their skin. However, city-dwellers are not entirely safe — the dust on sidewalks and streets may contain just as much of the bacteria.

C. tetani is harmless when present in soil or on the skin because it can only thrive in environments with little to no oxygen. A puncture wound, like one caused by stepping on a nail, creates the perfect environment for it to grow. Inside the wound, C. tetani releases a powerful neurotoxin called tetanospasmin, which may be the second most potent toxin, after botulinum. Even a small amount of tetanospasmin is enough to trigger the muscle spasms and contractions that define tetanus by affecting the nerves.

Why Puncture Wounds Are Ideal for Bacteria Growth

Rust itself doesn’t carry C. tetani; rather, it’s believed that a rusty nail has likely been exposed to soil that contains the bacteria. The crevices in the rust provide a hiding spot for the bacteria, and the deep puncture wound offers a perfect entry point for it to take action. However, any puncture wound should be taken seriously, no matter how clean the object that caused it may seem — this includes gunshot wounds and stabbings.

While deeper wounds provide the ideal conditions for infection, don’t disregard surface injuries. Any wound, whether caused by a sewing needle, gardening tool, animal bite, or scratch, carries the risk of tetanus. People who perform their own tattoos or piercings, as well as intravenous drug users, are also at risk. In short, tetanus isn’t limited to stepping on a nail. Always seek medical attention for a tetanus shot if you sustain a puncture wound and haven’t had a recent booster.

Why Cleaning a Puncture Wound Isn't Enough

If you step on a rusty nail or sustain a similar injury, keep in mind that the spores of C. tetani are resistant to common antiseptics used for wound cleaning. You’ll need to go to the hospital for an antitoxin called tetanus immune globulin. This antitoxin must be administered as soon as possible after the injury because it can only target circulating toxins, not the tetanospasmin that may have already attached to a nerve ending. Those who don’t get medical help risk their body locking up completely. The intensive treatment may involve sedatives, muscle relaxants, a quiet, non-stimulating environment for recovery, and possibly surgery.