August 03, 2022 5 min read
In the equestrian world, there are a lot of old wive’s tales that are continuously discussed and disproven time and time again. While there is not a lot of peer-reviewed, scientific research into these urban legends, there always seems to be plenty of anecdotal evidence floating around various barns and stables.
The one we’re going to explore today is the idea that light-colored horses are more prone to scratches than bay or black horses. The real question is whether this is actually true or if we just notice the symptoms of scratches more on lighter-colored horses and white legs than on the darker skin of other coat colors. After all, it is easier to notice hair loss and red, irritated skin on a light-colored background.
Are gray horses more prone to scratches? Let’s discover the truth.
Sunburn or photosensitivity is one possible cause of scratches in horses. Many owners of gray horses or horses with white markings are no strangers to applying sunscreen to their horse's light-colored, sensitive muzzle. But can sun damage on your horse’s pasterns really turn into scratches?
According to the Purdue University College of Veterinary Medicine, “Horses with white legs are at risk [of scratches] because unpigmented skin is more susceptible to sun damage.” Coming from a reputable source, this information certainly has weight. But unfortunately, there are very few studies out there that research the relationship between white legs, sunburn, and pastern dermatitis. However, there is a lot of research exploring the relationship between skin color and sunburn in humans, which can help us understand what may be happening with our gray horses.
One article in the peer-reviewed journal Photochemical and Photobiological Sciences explored the impact of darker skin in humans and susceptibility to sunburn. According to this article, those with fair skin are 70 times more likely to develop skin cancer. The researchers also concluded that melanin acts as a sort of “natural sunscreen” and is able to serve as a physical barrier that scatters UV rays and also acts as a filter that reduces UV penetration into the skin.
While studies exploring a direct link to pastern dermatitis and sunburn are rare, it is widely known that continued exposure to UV rays is related to a wide range of skin disorders, from blistering to melanomas. The bacteria and fungi that may cause scratches are opportunistic and will take advantage of any break or weakening of the skin barrier to take root. Sun damage, which is more likely on lighter-colored skin, may be another method of weakening the dermal barrier. In short, the claim that sunburn, which gray horses are more prone to, can cause pastern dermatitis is accurate.
If you have a friend who just bought a gray horse, an excellent congratulatory gift would be the largest bottle of whitening shampoo you can find. Equestrians who own or care for lighter-colored horses are plagued by manure and urine stains, caked on mud, and more. For bay or dark-colored horses, all of these stains would blend in and hide. But it can be a real challenge keeping a gray horse white.
Some horse owners are tempted to bathe their horses several times a week. Unfortunately, overbathing may make your horse look great, but it can actually have serious consequences. When we bathe our horses with strong soaps and stain removers, we’re stripping the skin of its natural oils. These natural oils serve to moisturize, protect, and nourish our horse’s skin. Just like your skin may feel dry after taking a bath, swimming, or getting out of the shower, our horse’s skin dries out the more you bathe them.
If you’re overbathing your horse, you may be cleaning their coat, but you’re weakening the protective dermal barrier. This makes it easier for the horse to develop abrasions, which in turn makes it easier for bacteria, fungi, and parasites to settle in. While you may think you’re taking excellent care of your gray horse, overbathing can actually create the perfect conditions for scratches to develop.
So far, we know that owners are more likely to bathe gray horses more often which can lead to scratches, and light-colored skin is more susceptible to sun damage which can allow bacteria to enter the skin. Both of these factors are unique to gray or light-colored horses, but let’s explore one more avenue. What if the development of scratches in horses doesn’t actually have anything to do with the color of the skin or coat, but actually has to do with their genetics?
Horses that were bred to be gray or have more chrome could be carrying a gene that predisposes them to scratches and other skin issues. It may not actually be about environmental factors related to coat color (overbathing, sunburn) but is actually related to the genetics of gray horses. While there are very few, if any, studies exploring the relationship between genetics and pastern dermatitis specifically, there are several other skin disorders that have been found to have a genetic component.
One such disease is the presence of melanomas in gray horses. One review article looked at several different studies performed by researchers on the subject and found that 80 percent of gray coat horses will develop melanoma after 15 years of age. On top of this strong correlation between gray coats and melanomas, recent studies in Spanish Purebred horses, which are traditionally gray, indicate that there is a genetic link between melanoma and vitiligo.
Researchers have even been able to tie the relationship between genetics and melanomas to a specific gene. A study found that if the gene for the gray phenotype had a higher rate of duplication, these horses would suffer from more aggressive melanomas.
In conclusion, the review article stated “Often, there is a genetic component involved in skin disease development.” While it is an extrapolation, it is possible that scratches could follow the same genetic relationship as melanomas in gray horses.
While few studies are available to prove that gray horses are more susceptible to scratches, one study did provide an interesting look at the correlation between increased white leg markings and pastern dermatitis in one breed of horse.
This study specifically researched the French-Montagnes breed, which has been seeing an increased number of breeders who are producing horses with more white markings. The researchers worked with a population of 974 horses, all of whom were examined at the field and station tests organized by the FM breeding association.
Take a look at the results:
In the conclusion, researchers stated “FM horses with more pronounced white markings have an increased risk to suffer from pastern dermatitis, sunburns, and hoof horn abnormalities.”
This study must be taken with a grain of salt, as it has a relatively small population size and would need to be repeated with various other breeds. Still, it draws an interesting conclusion that gives more weight to the idea that gray and light-colored horses could actually be more prone to scratches.
In a word, probably. This might just be one wive's tale that holds weight. Whether or not the increased presence of scratches in gray horses is due to environmental factors, like sunburn and overbathing, genetic factors, or a combination of the two, the fact remains that if you own or care for a gray horse, you’re more likely to be faced with pastern dermatitis at one point or another.
When it comes to managing cases of pastern dermatitis, it’s important to use non-toxic products that won’t harm healthy tissue. Zarasyl contains a high-tech amorphous silica formula tailored to promote overall skin health.
Click here to read more about Pastern Dermatitis.