September 06, 2021 5 min read
What’s your earliest memory involving petroleum jelly? This innocuous little tub of opaque goop has been around for decades. Equestrians use it to keep flies away. Beauty gurus have dubbed it the next skin care hack. Most families have had a tub of petroleum jelly in their cabinet since great grandma first used it on dry nostrils or a squeaky door hinge. It’s also used as the base for many commercial barrier creams for horses. This slimy substance has been used for a wide variety of purposes around the house and in the stable for over 200 years. But does it deserve its pedestal status? Is it really safe to use on our horses?
Petroleum jelly is derived from crude oil, a carcinogen and a substance known to be toxic to livestock. Originally, petroleum jelly was discovered in the early 1800s as a byproduct on oil rigs. Called “rod wax,” workers used it on the cuts and burns they got around the rig. It’s not exactly the clean and tidy origin story you would expect for a substance that is used in today’s beauty products.
Petroleum jelly’s main function is to seal off the skin from the external environment. By sealing off the dermal barrier, petroleum jelly traps existing moisture on the skin and stops evaporation. These sealant properties cause many to believe that petroleum jelly has great moisturizing properties. This is not completely true. Because it is not a humectant, it doesn’t give additional moisture to the skin, and can actually exacerbate dryness by preventing moisturizing solutions and water in the environment from reaching the skin. So, while it does stop water from evaporating, it only gives the illusion of shiny healthy skin, without actually increasing the moisture content.
Petroleum jelly’s ability to seal the dermal barrier extends far beyond just trapping moisture. The seal created by petroleum jelly is so impermeable that it starves the area of oxygen, which allows any oxygen-hating bacteria on the skin to survive undisturbed for longer. If the area is not cleaned properly prior to applying petroleum jelly, existing bacteria and fungal spores can easily proliferate and cause secondary infections. If you’re treating a case of pastern dermatitis or habronemiasis, the last thing you want to do is trap bacteria next to an open wound. An oxygen-free environment plus bacteria plus a weakened skin barrier could easily lead to secondary infections like cellulitis.
Certain skin conditions can actually be prolonged by the use of petroleum jelly or similar mineral oils. For example, the bacteria that causes rain rot, dermatophilus congolensis, can lay dormant through the winter months. Many horse owners will attempt to manage the condition with a product containing petroleum, such as mineral oil. Unfortunately, this only seals the bacteria next to the skin over the cold winter and through the dormant period. When the bacteria begins to proliferate once again in the spring, the horse’s rain rot will often be worse than the prior year as the bacteria will have had a much longer incubation period.
Because it is derived from crude oil, barrier creams for horses that use petroleum jelly can contain toxic ingredients like carcinogens. When refined properly, this is not a problem as all impurities are removed from the jelly. Unfortunately, refining requirements are not as strict in the United States, meaning that some petroleum products can be contaminated.
Another caution when using petroleum jelly is the possibility of internal ingestion. Ingestion can cause excessive salivation and abnormal stool. It’s important not to use it where your horse or his paddock mate can lick it off.
When buying a barrier cream for horses look for one that uses PEG instead of petroleum jelly. Polyethylene glycol, also known as PEG, is a better substitute to petroleum jelly as it strengthens the dermal barrier, instead of just creating the illusion of healthy skin. PEG is the combination of condensed ethylene oxide and water and is used for industrial, cosmetic, and medical purposes. It’s often used as surfactants, emulsifiers, cleansing agents, humectants, and skin conditioners because it’s hydrophilic, meaning that it is attracted to water. It’s a favorite for topical dermatological preparations as its hydrophilic properties means that it is excellent at penetrating the dermal barrier.
PEG’s powerful formula was demonstrated in a 2011 study reviewing its role in allograft transplantation. Ischemia reperfusion injury (IRI) is a common negative outcome that can occur when transplanting organs. In an effort to prevent IRI, researchers evaluated the use of a PEG formula to prevent tissue damage. The results of their study revealed that organs preserved with PEG “showed low fibrosis, transforming growth factor-β expression and apoptosis compared with the other groups.” PEG’s excellent preservative powers in this instance are due to its ability to seal cell membranes, which reduces cellular death or atrophy.
In a barrier cream for horses, PEG creates an external layer between the skin and foreign agents, like dirt and bacteria. Unlike petroleum jelly, the shield created by PEG not only prevents invasion by bacteria, it also reduces the impact of antigens. Antigens are defined as any foreign substance that “induces the immune system to produce antibodies against it.” This includes chemicals, pollen, bacteria, fungal spores, and toxins.
Immunogenicity is the response of the immune system against therapeutic treatment, which results in the creation of anti-drug-antibodies that can cause adverse side effects. Barrier creams for horses that use PEG actually prevent immunogenicity by conducting medications easily through the dermal barrier. The conjugation of PEG with therapeutic treatments increases their water solubility which in turn decreases their interactions with the immune system.
To simplify, think of PEG as a guide for medication. With its guidance, therapeutic drugs that may normally face pushback from the immune system are able to sneak across borders into the body. There they can work at full effectiveness without having been degraded by fighting with the immune system.
Equine wound healing can be a long slow process, particularly for issues involving parasites such as habronemiasis. A good barrier cream for horses that contains PEG can actually help to avoid wound chronicity. Wound chronicity can be induced by a process called proteolysis. Proteolysis is the process by which proteins are broken down into proteases. Proteases and their counterpoints, inhibitors, work together to heal wounds in a timely manner. However if this ratio of proteases and inhibitors is disrupted and too many proteases are created, a non-healing wound can develop. PEG prevents proteins from breaking down into proteases, thereby avoiding wound chronicity.
As equestrians, we all want the best for our four-legged companions. Learning about what we’re putting on their skin makes us more knowledgeable equestrians and better horse owners. At Zarasyl, we aim to take the frustration out of equine skin issues. Containing no steroids or antibiotics, we have created an FEI & race-day safe high-tech amorphous silica formula tailored to promote wound healing and overall skin health. You won’t find petroleum jelly in our barrier cream for horses, instead we use PEG 400 and PEG 3350 so you can rest easy knowing your horse is getting the best with Zarasyl Equine Barrier Cream.