Lockjaw, the common name for tetanus, happens when a toxin-producing bacterium called Clostridium tetani enters your body through a break in the skin. The bacteria live in soil, dust, and animal manure, and they’re found virtually everywhere in the environment. Once inside a wound, they produce a powerful toxin that travels to your nervous system and causes severe, uncontrollable muscle spasms, starting with the jaw muscles that give the disease its nickname.
How the Bacteria Get Into Your Body
Tetanus spores sit dormant in the environment, waiting for the right conditions to grow. They enter through broken skin, and certain types of wounds create a much more favorable environment for the bacteria than others.
The highest-risk wounds include puncture wounds (like stepping on a nail or thorn), cuts contaminated with dirt, feces, or saliva, and injuries where tissue has died, such as burns, crush injuries, and frostbite. These wounds share a common feature: they limit oxygen exposure deep inside the tissue. Tetanus bacteria thrive in low-oxygen environments, which is why a deep, narrow puncture wound is far more dangerous than a shallow scrape.
Less obvious routes of infection include chronic skin ulcers, dental infections, insect bites, intravenous drug use, and even surgical procedures. Any break in the skin can theoretically allow the bacteria in, but clean, minor wounds pose a much lower risk than dirty or deep ones.
What the Toxin Does to Your Muscles
Once Clostridium tetani starts growing inside a wound, it produces a toxin called tetanospasmin. This toxin travels along your nerves to the spinal cord and brain, where it blocks the release of chemicals that normally tell your muscles to relax. Specifically, it prevents nerve endings from releasing two key calming signals. Without those signals, your motor neurons fire without any brakes. Muscles on both sides of a joint contract at the same time, locking the joint in place rather than allowing normal movement.
This is why the jaw is often affected first. The muscles that control chewing are relatively short and close to the spinal cord, so the toxin reaches them quickly. From there, stiffness typically spreads to the neck, shoulders, back, and limbs. In severe cases, the spasms can be strong enough to fracture bones.
Symptoms and How Quickly They Appear
The incubation period ranges from 3 to 21 days after the bacteria enter a wound, with an average of about 8 days. Many people don’t even remember the original injury by the time symptoms start, especially if it was a small puncture or scratch.
The first sign is usually stiffness in the jaw, making it difficult to open your mouth or chew. This progresses to neck stiffness, difficulty swallowing, and rigidity in the abdominal muscles. As the toxin spreads further, painful whole-body spasms can be triggered by minor stimuli like a loud noise, a touch, or even a draft of air. Fever, sweating, and elevated blood pressure often accompany the muscle symptoms.
How Rare and How Serious It Is
In the United States, tetanus is extremely rare thanks to widespread vaccination. Between 2009 and 2023, an average of about 27 cases were reported each year across the entire country, with roughly 2 to 3 deaths annually. But rarity doesn’t mean it’s mild. Approximately 1 in 10 people who develop tetanus die from it, and the case-fatality rate is highest among older adults. The 2014 season saw 25 cases and 5 deaths, a 20% fatality rate for that year.
Most cases in the U.S. occur in people who were never vaccinated or who fell behind on their booster shots.
Other Causes of a Locked Jaw
Not every case of jaw stiffness is tetanus. The medical term for restricted jaw opening is trismus, and it has several non-infectious causes. Temporomandibular joint disorder (TMD) is one of the most common, causing pain, clicking, and limited movement in the jaw joint. Wisdom tooth removal can also trigger trismus because having your jaw held open during surgery strains the surrounding muscles. Head and neck cancer treatments, including radiation therapy, sometimes cause long-term jaw tightness as well. Trauma to the jaw, inflammatory conditions, and certain medications can all produce similar symptoms.
The key difference is context. Tetanus-related lockjaw typically follows a wound, comes with progressive stiffness spreading beyond the jaw, and worsens over hours to days. TMD-related stiffness tends to be chronic, often one-sided, and doesn’t come with fever or full-body muscle rigidity.
How Tetanus Is Treated
Once symptoms appear, treatment focuses on neutralizing the toxin that hasn’t yet attached to nerve tissue and managing the spasms while the body slowly recovers. A dose of tetanus immune globulin (TIG) is given by injection to bind and remove circulating toxin, but it can’t reverse damage the toxin has already done to nerve endings. Antibiotics are used to kill any remaining bacteria in the wound and stop further toxin production. The wound itself is cleaned and any dead tissue is removed to eliminate the oxygen-poor environment the bacteria need.
Patients with moderate to severe tetanus typically need intensive hospital care, sometimes for several weeks. Medications to control spasms, breathing support, and careful monitoring are standard. Recovery is slow because the body has to grow new nerve connections to replace those damaged by the toxin.
How Vaccination Prevents It
The tetanus vaccine is the single most effective way to prevent lockjaw. Children receive a series of shots during infancy and early childhood, with a booster in adolescence. After that, the CDC recommends a booster every 10 years for all adults. If you can’t remember your last tetanus shot, you’re likely due for one.
When you get a dirty or deep wound, your doctor may give you a booster on the spot if your vaccination isn’t current. This is especially important for puncture wounds, animal bites, or any injury involving soil or rust. The vaccine doesn’t treat an active infection, but keeping your immunity current means your body can neutralize the toxin before it ever reaches your nervous system.