Ringworm in Show Cattle: Why It Hits in Winter and What Actually Works

September 3, 2026 | True North Technologies | Stock Show Blogs

The calves are home. The clippers are put away for a few weeks, the hoods are going on at night, and everything is pointed at a spring major that feels a long way off right now.

That is exactly when it starts. Not in the show barn in March. In your barn, in December, in the dark.

If you have already found it, a grey crusty circle up on the face or the neck that was not there last week, skip ahead to the treatment section. If you have not found it yet, this is the article to read now, because ringworm in show cattle is a winter problem that gets discovered in the spring, and by then you are working against a clock you cannot move.

What ringworm in cattle actually is

Ringworm is not a worm. It is a fungal infection of the skin, and in cattle it is almost always an organism called Trichophyton verrucosum.

That fungus lives on keratin, which is the protein hide and hair are built out of. That is the whole disease in one sentence. It is not attacking your heifer the way a bacteria does. It is eating the outer layer of skin and the base of the hair fiber.

What you see follows directly from that. The skin under attack releases fluid, that fluid dries on the surface into the crust you can feel, and once the fungus has finished the keratin underneath, the crust lifts and falls off, taking the hair with it and leaving a bare grey patch behind.

And it does not stay put. It works outward in a circle. It finishes the keratin in the middle, moves to the ring of fresh skin just outside it, and does the same thing again. That is why a spot the size of a quarter in December is the size of your palm in February, and it is why the live fungus is always out at the advancing edge and never in the middle. Remember that, because it decides where you spray.

If you run sheep alongside your cattle, this is the same family of organism behind club lamb fungus, and the protocol below is the one we use there too. The seasons and the barn conditions differ enough to be worth reading separately.

Why winter, and why your barn

Ask any large animal veterinarian when they see cattle ringworm and they will tell you winter, every time. That is not a coincidence and it is not bad luck. Winter hands this fungus everything it wants.

No sunlight. Ultraviolet light is hard on dermatophytes. Cattle standing out in July sun are getting a free treatment every day. Cattle in a barn in January are not.
Long hair holding moisture. Hair that stays damp against the skin is a better place to live than hair that dries out in an hour.
Close confinement. Cattle housed together all winter, sharing air, panels, gates and tie rails.
Young cattle. Calves and yearlings get it worse than mature cattle do, and a show string is nothing but young cattle.

Now add what a show barn does on top of a normal winter barn.

Clipping. Every clipping leaves thousands of small abrasions you cannot see. That is the door in.
Washing. Show cattle get rinsed and washed on a schedule no pasture calf will ever see. Shampoo does not know the difference between dirt and the natural oils on the skin, so it takes both. Those oils are part of the skin barrier, and they help hold the normal population of organisms that lives on healthy skin and takes up the space an invader would want. Wash often and you are left with a barer surface and a changed skin microbiome sitting on top of it.
Hoods. Warm, dark, damp, and in contact with the skin for hours at a time.
Shared equipment, and your own hands. Combs, brushes, blowers, clipper blades, chutes, the show box, the trailer. Spores live on all of it for months. And you move it too. Work an affected calf and then go put your hands on the next one down the line, and you carried it yourself. Nobody counts that one because it does not feel like equipment.

And this is how it starts in July

Everything above is why ringworm is a winter disease. Now here is the part that catches show families, because it is the exception nobody watches for.

Go back and read what this fungus wants. No sunlight. Damp hair held against the skin. Cool, still air. Animals in close quarters. Now think about what a cool room is.

Dark. Cool. Damp. Poor air movement compared to outside. Cattle standing close together. Hair held long and held damp on purpose, for weeks at a stretch.

A cool room is winter, in July. You built it to hold hair through the heat, and it works, and the same conditions that hold hair are close to the conditions this fungus is looking for.

That is why show cattle can break with ringworm completely out of season, in the middle of summer, when nobody is looking for it. And out of season is exactly when it gets missed, because everybody knows ringworm is a winter problem, so a grey crusty spot in August gets called something else for three weeks while it doubles in size.

I am not telling you to shut off your cool room. It is how hair gets grown and I know exactly what it is worth to you. What I am telling you is to stop treating the room as neutral. Keep it as clean and dry as a cool room can be, bedding changed and no standing damp, get real air movement through it, and watch hides in the summer the same way you watch them in January.

There is an honest tradeoff underneath this and it is worth saying out loud. Sunlight genuinely works against this fungus, and it also works against the hair you are trying to hold. Nobody gets both, and anybody who tells you otherwise has not run a show string. You are choosing hair, which is a reasonable choice. Just go in knowing what the choice costs you and manage the rest.

What it looks like on cattle

Classic cattle ringworm shows up on the head and face, especially around the eyes, and on the neck, ears, and along the topline and shoulder. What you see is usually:

Grey or chalky-white circular crusts, raised and rough, often described as looking like a coin stuck to the hide. These are not warts and they are not a growth. It is your calf’s own skin weeping under the fungus and that fluid drying on the surface.
Hair that pulls away easily from the spot, and bare skin where the crust has already lifted off
Round lesions that keep getting bigger, sometimes with rings inside of rings. That expanding circle is the most useful thing you can look at. A spot that is growing week over week is an active spot.
Not much itching, and usually a calf that otherwise acts completely normal and eats fine

What it gets confused with

There are a couple of things that sometimes get confused with this, and they are treated differently.

Lice are the big one in winter, and they are far more common than ringworm. Lice make cattle rub, and rubbing makes bare patches. The difference is behavior: a lousy calf is itchy and will not leave a rub post alone, and a ringworm calf mostly ignores it.

Warts, which are a virus, actually are growths, and that is the honest way to tell them from a ringworm crust. A wart is tissue growing up off the hide. A ringworm crust is dried fluid sitting on top of it.

I have watched families treat lice for a month on a calf that had ringworm, and treat ringworm on a calf that was crawling with lice. Both cost the same thing, which is time you do not get back before a show.

Get a diagnosis

Call your veterinarian and get the lesion looked at.

You need to know which of those things you have, and early on you often cannot tell by eye. A culture or a PCR is the only way to be certain. One honest note: the black light trick does not work here. That test picks up a different fungus, and Trichophyton verrucosum generally does not fluoresce at all, so a dark spot under a Woods lamp does not clear your calf.

Your vet may also reach for something stronger than what is in this article. Lime sulfur and miconazole are what the veterinary literature supports most strongly for dermatophytes, and if the lesions are widespread or a major is close, that conversation needs to happen now rather than after a month of doing it yourself.

Everything below is barn management that works alongside your veterinarian’s plan, not instead of it.

It goes both ways, so protect your kid

I will not soften this part. Ringworm in cattle is zoonotic. It transmits to people, and Trichophyton verrucosum is one of the more aggressive ones for humans. It transmits to kids who are handling cattle every day with their forearms bare.

On a person it shows up as a red, scaly, expanding ring, usually on the forearms, hands, neck or face.

Long sleeves and disposable gloves any time somebody works an affected calf
Wash hands and forearms thoroughly afterward, every time
Do not share towels, and wash barn clothes separately in hot water
If a ring shows up on a person, that is a call to your family doctor

Tell the kids why. In my experience they are better about it than the adults are once somebody explains it.

The two jobs, and why one product cannot do both

Working a fungus problem on show cattle is two separate jobs, and people fail because they only do one.

Job one is the surface. Reduce what is living on the hide and on everything the calf touches. That is an antiseptic job, and that is what chlorhexidine is for.

Job two is the skin itself. A dermatophyte gets in through skin that is dry, abraded and run down, and in a show barn we are actively producing that skin every time we clip and every time we wash. Skin that is well supported, with a healthy barrier and a healthy population of the normal organisms that live on it, is a much harder surface to colonize. That is a skin support job, and it is what Provilli is for.

Put plainly: the shampoo takes the oils and the microbiome off, and Provilli improves the skin microbiome, which is how you put that back. That is why it belongs in the same bottle as the antiseptic instead of being a separate thing you get around to.

Those two jobs are the whole program when you are preventing. When you already have an active infection, a third layer goes on top of them, and I will walk through how that stacks in the treatment section.

The mix

One quart sprayer. Into it:

1 ounce of Provilli
1 ounce of 2 percent chlorhexidine solution
Fill the rest with water

Shake it before every use. Provilli is an emulsified product and it will want to separate sitting on a shelf.

Same bottle whether you are preventing or treating. What changes is how often you use it and what else goes on alongside it.

The prevention protocol

Prevention is where winter is won, because a lesion you find in February started weeks earlier and the hair will not be back before spring.

Spray after every clipping and after every wash. This is the single highest value habit on the list and it covers both doors at once. Clipping opens abrasions. Washing strips the oils and the microbiome. Either one leaves that calf more exposed than he was that morning, so the spray goes on at the end of both jobs.
Spray coming home from every show or hauling trip. The day you unload, not the day you find something. If you run lambs or goats too, that same haul-home moment is the one that matters for worms and coccidia in small stock, which is a separate piece.
Twice a week through the winter as a baseline, on the face, neck, ears and topline, which is where this shows up first.
Put your eyes on the hide at every feeding. You are out there morning and night anyway. Look at the face and neck under good light, and part the hair on the topline. Catching one spot beats catching nine.
Any time the cool room is running, keep it as dry and clean as a cool room can be. Bedding dry and changed, real air movement, and no standing damp. You cannot make it sunny, but you can keep it from being a swamp, and that is the summer half of this problem.
Hoods get washed hot, on a schedule. A hood sits against the skin for hours in exactly the conditions this fungus likes, right over the face and neck where ringworm shows up first, and almost nobody launders them often enough.
Disinfect combs, brushes and blades between animals, every time. If you skip this you will reinfect a calf you just cleaned up and never understand why nothing is working.
Do not share equipment, and mind the order you work them in. Anything questionable gets handled last, every chore. Your hands move this as reliably as a dirty comb does.

The treatment protocol

You found a spot, your veterinarian has confirmed what it is, and you are working it.

Isolate that calf. Separate pen, separate equipment, and work him last at every chore.
Leave the crusts alone. This is the instruction people ignore and it is the one that costs them the most. Do not pick at them, do not scrape them, do not scrub them off, and do not go after them with a brush, a comb or a rice root. I know how badly you want that spot gone. Working a crust tears the skin underneath it, and torn skin is one more door for the fungus and an open invitation for a bacterial infection on top of the fungal one. It also puts infective material on your hands and your equipment. Let the crust release on its own when the skin under it is ready.
Spray the lesions and a wide margin around them. Wider than you think. The live fungus is out at the advancing edge of that circle, working into hide that still looks completely normal to you. If you only treat the crust in the middle you are treating the part that is already finished.
Let it air dry. Do not blow it out. Two reasons and both matter. A blower on a calf with active lesions is broadcasting infective material through your barn, onto your other cattle, your equipment and your kid. And blowing takes the solution back off before it has had any contact time, which was most of the point. In a cold barn or a cool room this takes longer than you would like. Let it take longer.
Once it is dry, top it with your treatment of choice on the affected areas. Fluid film, MTG, or whatever your veterinarian recommends. That goes on the lesions themselves, and it is the layer doing the work of killing the fungus. Follow the directions on whatever you are using.
Then leave it sit. Do not wipe it, do not rinse it, do not blow it. These products work by staying in contact with the skin, so contact time is the whole point.
Run that sequence twice a day. Spray, air dry, top, leave it. It only works in that order.
Keep going after it looks better. The skin closes up before the fungus is gone. Stay on it for two full weeks past the last visible lesion, or as long as your veterinarian tells you.
Keep spraying the healthy cattle on the prevention schedule the whole time, because the exposure already happened.
Strip and disinfect while you treat. Bedding out, pens and panels disinfected, hoods washed hot, combs and blades disinfected after every single use. Spores outlive your treatment plan by a wide margin.

The lever nobody funds

Everything above happens on the outside of the calf. The chlorhexidine works on the surface, Provilli works on the skin, your topper works on the lesion. All of it matters and none of it is optional. But the outside is not what finishes this. The animal does.

Think about the levers you actually have on any health problem in a barn. There are four. Management, vaccination, treatment, and the immune system. The first three all run through the fourth, because a vaccine needs an immune system to answer it and a treatment needs one to finish up behind it. The immune system is the only one of the four that nobody budgets for. It is the lever everybody leans on and nobody feeds.

That idea is not theory for me. Back when we were first developing PreVent, I bought a set of lambs that had been disqualified at a fair over fungus and worked on them with nothing but immune modulators, because I wanted to see what an animal’s own immune system would do with this problem if somebody actually fed it. That work became part of the original research behind PreVent. Same organism family, same question.

For show cattle, TrueGlo or TrueGlo CR is where that lever gets fed, daily, in the bunk. Both are built on PreVent, both support gut health and immune function, and both are multi species, so they are right for cattle. They go alongside the topical program, not instead of it. Worth saying plainly, since families ask: the Turbo and Turbo Shag versions are show pig products, so those are not the ones you want for a calf.

I am not going to tell you a feed supplement is the answer to a fungus. Go back and read the treatment section, because that is the work. What I will tell you is that the calf doing the healing is the one variable in this whole article that most families never think to support.

What to expect, and the hard line on showing

Dermatophyte infections are slow. Skin turns over slowly, hair grows back slower than that, and nobody honest is going to tell you a calf clears up in a weekend. Over two to four weeks what you want is the boring good stuff: no new spots, and the existing circles holding still instead of growing. Measure the edge, do not judge the middle. A crust that lifts off is the normal course of the thing. A lesion that has stopped getting bigger is the sign you are winning.

Now the part nobody wants to read, and I would rather you hear it from me in December than from a vet at a check-in gate in March. A calf with an active lesion does not go to a show. Not until it is healed and the hair is starting to come back.

That is not primarily a rule book answer, although the majors do inspect and cattle absolutely get turned away. It is that an active lesion is contagious to every calf on that tie-out and to every kid handling them. Hauling him is how one spot on one calf becomes a problem in twenty barns, and those are your friends.

The hair is your signal. Skin that has quieted down but is still bare has not finished. Hair starting to fill the patch back in is what tells you the skin underneath actually recovered.

Read that timeline backward and you have the argument for everything in the prevention section. Hair does not hurry, and winter is short. If a spot found in February can cost you a major in March, then the minute you spend spraying in November, on the weeks when nothing appears to be wrong, is not the cautious option. It is the only one that works on the calendar you actually live on.

The short version

Ringworm in show cattle is a keratin-eating fungus that gets in through hide you have just clipped and washed, and it moves around on shared equipment and on your hands. Winter is its season because there is no sunlight, the hair stays damp and the cattle are close together. And a cool room recreates all of that in July, which is how show cattle break with it out of season and get missed.

It transmits to your kids, so gloves and sleeves. Get a real diagnosis before you treat, because lice and warts both get confused with it.

Then run the two jobs. Chlorhexidine for what is on the calf, Provilli for the calf’s own skin, one quart bottle, an ounce of each. Spray after every clipping, every wash and every haul home, wash the hoods, disinfect your combs like it matters, and put your eyes on the hide at every feeding. When you are treating an active spot, the order is spray, air dry, top with your treatment of choice, and leave it sit.

And do not forget the animal underneath all of it. Everything in that bottle works on the outside; the calf is the one who finishes this, which is why the immune system is worth feeding on purpose.

Know the hard line going in too: a calf with an active lesion does not go to a show, not until it is healed and the hair is coming back. Hair does not hurry, which is the whole reason prevention is the real work.

That is not a miracle. It is a minute at chores, done in December, when nothing appears to be wrong. Which is exactly when it is working.

Questions about whether this fits your program? Reach out. We are glad to talk it through, no sales pitch.

Frequently asked questions about ringworm in show cattle

What causes ringworm in cattle?
A fungus, not a worm. In cattle it is almost always Trichophyton verrucosum, a dermatophyte that feeds on the keratin in hide and hair. The skin releases fluid in response, that fluid dries into the crust you see, and the crust falls off once the fungus has finished the keratin under it, leaving a bare patch. The lesion then expands outward in a circle, which is where the name ringworm comes from.

Why does cattle ringworm always show up in the winter?
Winter gives the fungus everything it wants. There is no ultraviolet light, which is genuinely hard on dermatophytes, the hair is long and holds moisture against the skin, and cattle are confined close together. Young cattle are the most susceptible, and a show string is all young cattle. In a show barn, clipping, washing and hoods stack on top of all of that.

Can show cattle get ringworm in the summer?
Yes, and a cool room is usually why. A cool room is dark, cool and damp with limited air movement, cattle in close quarters, and hair deliberately held long and damp, which is close to a list of what this fungus wants. It is winter conditions in July. That is why show cattle break with ringworm out of season, and out of season is when it gets missed, because everybody knows ringworm is a winter problem. Nobody is telling you to shut the room off, because it is how hair gets grown. Keep it dry and clean, get real air movement through it, launder hoods hot and often, and watch hides in August the way you watch them in January.

Can humans catch ringworm from cattle?
Yes, and Trichophyton verrucosum is one of the more aggressive ones in people. It appears as a red, scaly, expanding ring, usually on forearms, hands, neck or face. Wear gloves and long sleeves when handling an affected calf, wash thoroughly afterward, and see your family doctor if a ring appears on a person.

How do I tell ringworm from lice on a show calf?
Behavior is the quickest tell. Lice make cattle itchy, so a lousy calf rubs constantly and will not leave a post alone. A calf with ringworm usually ignores it. Lice are also far more common in winter. Warts are actual growths of tissue rather than dried crust, which is the cleanest way to tell those apart. Your veterinarian can culture the lesion if there is any doubt, and a black light is not a reliable test here.

What do you put on ringworm in show cattle?
The barn-level mix we use is one ounce of Provilli plus one ounce of 2 percent chlorhexidine solution in a quart sprayer, filled with water. Spray the lesions and a wide margin around them, let it air dry without a blower, then apply your treatment of choice on the affected areas, fluid film, MTG or whatever your veterinarian recommends, and leave it sit. Twice a day. Talk to your veterinarian first, because widespread cases or a show that is close may call for lime sulfur or miconazole.

Does Provilli treat ringworm?
Provilli is a nutritional supplement and grooming aid, not a medication, and we are not making a treatment claim with it. Diagnosing and treating a fungal infection is your veterinarian’s job, and Provilli goes alongside that plan rather than instead of it. What it does is work on the skin. Provilli improves the skin microbiome, and that matters more on show cattle than most people realize, because the clipping and washing that come with fitting are exactly what take that microbiome down. Customers running show cattle with fungus also tell us that adding Provilli gets hair back faster than they used to see. Worth knowing, since people ask: medium chain fatty acids are not a new idea. They have a long history in the research literature as antifungals, and that body of work is part of why we build with them.

How long does cattle ringworm take to clear up?
Plan on two to four weeks of consistent work before you can call it, and keep treating for about two weeks past the last visible lesion or as long as your veterinarian directs. Hair fills the bare patches in last and may not be back before your show, which is the strongest argument there is for running prevention all winter.

Can my calf still be shown?
No. Not until the fungus is healed and the hair is starting to grow back. An active lesion is contagious to every calf on that tie-out and to every kid handling them, and hauling him is how a whole barn full of families ends up with the same problem a month later. Hair filling the bare spot back in is your signal that the skin actually recovered, not just quieted down. Most majors inspect at check-in as well, so a calf who should not go often does not get in anyway.