Caring for horses during the UK winter can be challenging at the best of times, with short daylight hours, wet weather and muddy ground conditions. As we aim to keep our horses, ponies and donkeys as healthy as possible during winter, it is important to be aware of the risk of rain scald and mud fever infections, knowing how best to prevent these conditions and to recognise and treat them early if they do occur.  

Both rain scald and mud fever are skin infections, caused by the bacteria Dermatophilus congolensis. Rain scald typically describes the infection occurring over the body, neck and head, whereas mud fever (or greasy/cracked heel) refers to the same infection affecting the legs, usually around the fetlocks. 

What causes the infection? 

Dermatophilus congolensis bacteria are found on the surface of normal, healthy, equine skin, but when the skin becomes damaged or is softened by persistent dampness and warmth, these bacteria can get a little overzealous.  

Warm, wet conditions typically occur underneath heavy rugs on milder winter days, when sweat becomes trapped against the skin, or in persistently muddy field conditions, which can be very difficult to avoid during the winter months. 

What does rain scald / mud fever look like? 

Infection causes scabs to form on the surface of the skin, which clumps hair together into tufts. Over the body, head and neck, these will feel rough to touch, and hair may fall out in clumps like paintbrush bristles.  

There may be yellow ooze from the skin below, and often horses are uncomfortable being groomed as the skin is inflamed. When the legs are affected, similar scabs form but horses may also be lame and may even have swelling around the pastern too. 

If you are in any doubt about the diagnosis, or are treating recurrent or stubborn infections, please don’t hesitate to contact your vet. Similar tufts of hair can be lost due to fungal infections such as ringworm, or parasites including chorioptic mites. Underlying conditions such as Cushings disease may make a horse more susceptible to rain scald than normal. If necessary, your vet can take samples to confirm the diagnosis of rain scald or can test for other diseases.   

How is the infection treated? 

Unless there is severe infection (where antibiotics may be required), rain scald and mud fever can usually be treated topically, i.e. with antibacterial washes and creams. If at all possible, bring your horse into a warm, dry environment during treatment. If this is not available, try to get away from muddy areas and provide a waterproof rug.  

  1. Where the hair coat is very thick, it may be necessary to gently clip the affected area but be aware that this may be painful, and some horses will require sedation. 
  1. Start by removing scabs as the bacteria are hidden beneath. Warm soapy water can help loosen scabs, but it may take several sessions to clear large areas, especially if scabs are firmly attached. DO NOT just rip them off if they are large or well attached, as you will cause more damage, and potentially spread the bacteria deeper. 
  1. Once scabs are cleared, scrub affected areas using dilute antibacterial solutions such as chlorhexidine or iodine and leave this to work for 5-10 minutes.  
  1. Rinse the area with warm water and then dry thoroughly using a clean towel. 
  1. A barrier cream containing zinc oxide (like nappy rash creams) can then be applied to dry skin.  

Repeat this process once or twice daily until the infection is resolved and remember to contact your vet if things are not clearing up as expected – there may be an underlying cause.  

During treatment, avoid riding your horse as they may be uncomfortable due to the infection and consider giving anti-inflammatory medication in severe cases. Speak to your vet for guidance. 

Is the infection contagious? 

No… but also yes! Infection will not spread directly from your horse to other horses in the same field or yard, but sharing rugs, towels, tack or clippers can increase the risk of infection in other horses whose skin barrier is compromised, for example by persistent damp or if irritated by clippers. Disinfect all grooming brushes and clippers between uses to avoid spread or reinfection of your own horse during and after treatment. 

Can rain scald / mud fever be prevented? 

Given that Dermatophilus is a normal finding on healthy horse skin, and that rain and mud are normal findings during winter in the UK, it is not possible to completely prevent infection. We should, however, aim to and be able to reduce the likelihood and severity of infection by taking a few sensible precautions.  

Rain Scald 

  • Where possible, provide shelter during persistently wet conditions, either by stabling or providing field shelters and waterproof rugs. 
  • Understand your horse’s needs when it comes to rugs. Aim to protect from persistent cold and rain but avoid creating sweat. Rugs should be changed frequently and removed on milder days or when horses are stabled.  
  • Regularly brush away dried mud but do not overgroom as this may remove protective oils from the coat. Regular grooming also allows any infections that do occur to be identified and treated early. 

Mud Fever 

  • Avoid horses standing in muddy areas for long periods of time by;  
  • stabling for part of the day/night,  
  • fencing off or avoiding particularly muddy fields,  
  • moving hay feeders around to prevent poaching,  
  • checking automatic drinking troughs regularly for leaks,  
  • putting hardcore down in areas where horses gather, e.g. gateways or paths. 
  • Avoid washing your horse’s legs. Instead, allow mud to dry, then brush it off.  
  • Treat underlying conditions such as mites (common in heavily feathered legs). 

Horses do not build any immunity to Dermatophilus infection, so previous mud fever/rain scald episodes do not make future infections any less likely. Contact your vet to discuss any aspect of prevention, diagnosis and treatment, as they are best placed to understand your horse as an individual and will be happy to help advise.  

Further reading 

Edinburgh Vet School – Rain Scald and Mud Fever Factsheet 

XL vets – Rain Scald – includes photos 

British Horse Society – Rain Scald, Mud Fever and Rugging