Rusty Nails, Dirty Wounds and Tetanus

This morning I heard a newscaster lament, “I was cut with rusty metal, and there is a national shortage of tetanus vaccine.”

Despite his concerns, this is not exactly certain death. Growing up in Southern California, I spent most of my youth barefoot, tangled with more than a few rusty nails and was on the tetanus-shot-a-year plan. This experience prompted an interest in the whole rusty nail tetanus connection.

What about rusty nails and tetanus? Tetanus is actually caused by a germ, not by rust. This germ is in spore form and lives in the dirt. The technical name is clostridia tetani. Clostridia is a bad family of bugs; its relatives cause botulism and gas gangrene. Pretty unpleasant stuff.

Nailedphoto © 2005 Scott Robinson | more info (via: Wylio)
Rust is the oxidation product of iron. Oxidation is a form of chemical burning. You are familiar with this – this is what chlorine does to your swimming pool. It oxidizes germs, meaning it kills them. Rust is not infectious for anything, including tetanus. Yes, I said rust does not cause tetanus, and reading in the dark won’t ruin your eyes. So much for medical myths.

The concern is getting dirt in the wound, which may contain clostridia tetani spores. If these spores find a friendly environment in your wound, you can get tetanus. These spores don’t like a lot of oxygen, so wounds that have a lot of dead tissue, like road rash, are perfect for growing clostridia tetani. These spores also like wounds in the foot because the foot is a long way from the heart, so it doesn’t have the best blood flow.

There is the rusty nail connection. The nail was lying in the dirt, thus the rust. When you stepped on it, some dirt may have been pushed into the hole in your foot. Dirt in a foot wound is a good set up for tetanus. You could get tetanus from a plastic nail as long as dirt got into the wound.

If you get a few clostridia tetani spores in your wound and the conditions are just right, they will try to grow. If they succeed in growing, they will release a toxin that paralyzes your muscles. The lock-jaw will be the least of your problems; the lock-diaphragm stops your breathing. If you have had a tetanus shot recently, you have high levels of immunity that can kill these germs before they cause trouble. If you haven’t had a tetanus shot in 5 or 10 years, we give you a tetanus shot (usually TDap) and remind your immune system to get going. Once you have had a couple of tetanus shots, you can mount an immune response in a hurry when given a tetanus booster. Your body can actually make this protection faster than the clostridia spores can grow, so you’re safe.

syringephoto © 2006 connyx / crucify | more info (via: Wylio)

A tetanus shot (TDap) gives you great immunity for 5 years. Even in the presence of a dirty wound containing clostridia tetani, you are safe from tetanus.

For five to 10 years after a tetanus shot, you have partial immunity to tetanus, but it would be a race between the clostridia growing and your immune system fighting it. If the wound is clean, you don’t need a tetanus shot, as there is little or no risk of tetanus. If it is dirty (literally containing dirt), we will give you a tetanus shot, just to be safe.

The most common wound that is the source of tetanus in the U.S. is rose thorn wounds. You are gardening, so you have dirty hands, a rose thorn pokes you, and what self-respecting gardener worries about a rose thorn prick? You don’t even wash your hands. You just keep gardening. Perhaps not too surprising this can be the source of tetanus.

So get a tetanus shot (TDap) every decade or sooner for dirty wounds. Remember to promptly use soap and water to get any visible dirt out of a wound, even minor wounds. Gardeners especially – stay up on your tetanus immunizations.

Stay well,

Dr. B

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8 responses to “Rusty Nails, Dirty Wounds and Tetanus

  1. I have a question. I’ve been going to the Dr for the past year because of horrible muscle spasms all over my body. I get them in my feet, legs, hands, jaw, throat, back, chest and upper abdomen. I’ve been to the ER for the chest spasms too. All they ever did was prescribe muscle relaxers which are not very effective.

    I just switched Dr’s and so had another entire physical – after hearing my symptoms and reviewing my history she did two things – gave me a tetanus shot and referred me to a specialist for the muscle spasms.

    I went from having 10+ severe and really painful spasms per day to 0 since I got that shot 3 days ago.

    Could I have had tetanus or is this just a strange coincidence?

    If I had tetanus wouldn’t I be dead now?

    also, is it possible to have just enough immunity that the progression of the disease is slow, like in my case – and you live with tetanus for awhile until your immunity is diminished enough for it to get worse?

    I guess I’m hoping that this fixes my symptoms and we don’t have to keep trying to figure out the cause of my painful muscle spasms. Thanks for any info you can give.

    • Tetanus is an 95% fatal disease. The clostridia tetani spore makes a paralyzing neurotoxin and you stop breathing, quickly. It’s a nasty bugger. So your muscle pain would not be cured by anything i know about in the tetanus shot. Perhaps it gave your immune system something else to do, besides making your muscles hurt.

  2. if a rusty nail at home goes into your finger and there is no blood. Does one need a tetanus shot

    • The short answer is yes. The longer answer is it is not the object that breaks the skin, it is the opportunity for clostridia spores to get in the wound. Since these spores are in the dirt, a dirty cut is much more tetanus prone than a clean one. The “if it bleeds” is actually kind of interesting. Clostridia spores grow best in areas of poor circulation because they don’t like a lot of oxygen. A bloodless wound thus is more risky on a theoretical basis. Remember rose thorns are the number one culprit, even though they make trivial puncture wounds. The dirt in the wound is what counts.

  3. if i am building with a rusty claw hammer and the end sharp part just barely grazes my thumb barely enough to scab will i get a desiese such as tetanus or something else?

    • Check with your personal physician but if the wound is clean, this is a low risk wound. Tetanus comes from spores in the dirt, not rusty metal. Soap and water and keep an eye on it.

  4. I was sawing some wood with a hand saw. The saw was new, so no rust. I barely cut the skin on my finger in the process and I washed it with anti bacterial soap. It seemed to heal and close up within a mater of under an hour. I left it exposed and was putting some screws in the wood I cut and the screws were old and in a plastic jar. The screws rubbed against the cut, but it didnt open the wound. I washed it again and put neosporen on it and a bandaid over it. Will the neosporen kill the bacteria if it’s present? also, I have a scab on my knee that I picked and Im not sure if it healed before I was out in the garden on my knees. Is that a risk? I havent had a shot in probably about 10 years. If I put some neosporen on my knee, will that reduce the risk? I read that the spore likes enviorments with little oxygen. if I put neosporen and a bandaid over it, will that put me at more risk than leaving it exposed?
    Thank you!

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