Zinc ointment for horses: what zinc oxide does and where its limits lie

This article was created with the help of AI.

What is in a zinc ointment

A classic zinc ointment consists of highly concentrated zinc oxide worked into a fatty or waxy ointment base. This particular formulation gives the paste its typical white, thick and opaque consistency. Zinc oxide is one of the most common zinc sources in topical care.

In everyday stable practice, zinc paste is part of the familiar kit of almost every grooming box. The high pigment density of the zinc oxide it contains produces the characteristic covering effect, while the fat content mechanically protects the skin surface from external influences. In dermatology, topical zinc oxide preparations have long been used as agents that protect against light and soothe the skin. Nevertheless, the purely physical protective layer of a thick paste differs fundamentally from modern care approaches that rely on controlled delivery of the trace element.

• High solids content: finely ground zinc oxide is densely distributed in the ointment base and creates a visible white layer.
• Lipophilic fatty base: petroleum jelly, lanolin or plant waxes form the moisture-repellent carrier of the paste.
• Mechanical covering: the thick consistency remains on the skin surface as a physical protective barrier.

Why zinc oxide is not the same as zinc ions

For the care properties on the skin, only the charged ionic form of a metal matters, not the neutral metal in atomic or molecular form. Solubility studies show that zinc oxide is practically insoluble in water and dissolves primarily in acidic conditions, but hardly at all on the alkaline skin of the horse (pH 7.2 to 7.5). The amount of zinc ions released therefore depends heavily on the ambient conditions and is difficult to predict.

Conventional metal-based care products use chemical compounds such as zinc oxide. Before zinc ions can be released at all, the chemical bond between the zinc and the oxygen must first break. Zinc oxide is insoluble in water but, compared with other zinc compounds, has a high zinc content. Laboratory experiments with model fluids illustrate the strong dependence on pH: while around 90 percent of the mass dissolved within 24 hours in an acidic solution at pH 4.5, no dissolution was measurable in a neutral physiological solution at pH 7.4.

This finding matters greatly to horse owners, because equine skin differs fundamentally from the acidic skin of humans. In horses, the skin reacts alkaline, with values between 7.2 and 7.5. Precisely within this pH window, zinc oxide dissolves only to a limited extent. That does not, however, mean that no zinc ions reach the skin from a zinc ointment. In a controlled study of 30 healthy volunteers, a zinc oxide preparation released measurable quantities of zinc ions to the skin. The key insight is therefore not that zinc oxide is ineffective, but that the quantity released depends on local conditions and cannot be reliably predicted.

• Water insolubility: zinc oxide barely dissolves in pure water or in neutral fluids.
• pH dependence: zinc oxide dissolves quickly in acidic conditions, markedly more slowly in alkaline ones, and to an extent that is difficult to predict.
• Alkaline equine skin: at values of pH 7.2 to 7.5, the horse's skin offers no acidic environment in which the compound would break apart easily.
• Unpredictable dosing: the amount of zinc ions released varies considerably with local moisture and friction.

What a zinc paste is useful for

As a physical barrier, a classic zinc paste performs a useful role in the daily stable routine. It reliably keeps moisture and damp away from vulnerable skin areas, and its dense white colour marks the cared-for spot mechanically. In situations where purely external protection from moisture is required, the ointment is a simple option.

When intact skin in the pastern fold needs protecting from muddy paddock ground or damp bedding, the paste's dense fatty film acts like a mechanical shield. Its high coverage also makes it easy to see at a glance whether the protective layer is still intact or has been rubbed off in the field. In dermatology, zinc oxide has long been a commonly used topical preparation.

• Protection from surface moisture: shields intact skin from damp, mud and urine in the stable or on the paddock.
• Visual check: makes it easier in daily routine to see whether the applied protective layer is still in place.
• Mechanical protection: offers simple coverage of intact skin against external irritants.

Where the limits lie

Despite its strengths as a barrier, the thick consistency of a zinc paste brings clear drawbacks in daily use. Tough paste layers cover the skin surface, collect stable dirt and are difficult to clean off.

A main problem with thick pastes is that skin changes beneath the covering layer are easily overlooked. In addition, bedding particles, sand and dirt become trapped in the greasy mass. Removing it often requires vigorous rubbing, which puts additional mechanical stress on sensitive or irritated skin. Another aspect is animal behaviour: the Merck Veterinary Manual names licking off applied topical preparations as a common route of ingestion in animals, with gastrointestinal upset among the typical consequences. Moreover, the manufacturers of many zinc pastes themselves note that the product is not intended for open wounds, deep cracks or weeping areas.

Property / role	What a zinc paste delivers	Where the limit lies
Physical protective layer	Forms a water-repellent fatty barrier on the skin	Can only be removed with vigorous rubbing
Visual check	Visible white marking of the treated area	Covers the skin beneath and makes the daily visual check harder
Release of zinc ions	Releases measurable amounts of zinc ions in the presence of moisture	The amount released on alkaline equine skin is not predictable
Area of use	Suitable for intact skin, scrapes and grazes	Not intended for open wounds, deep cracks or weeping areas

Zinc in feed is not the same as zinc on the skin

Topical skin care with zinc compounds must be strictly distinguished from internal zinc supply through the horse's feed. According to the recommendations of the National Research Council (Nutrient Requirements of Horses, 2007), the maintenance requirement of a mature horse weighing around 500 kg is approximately 400 mg of zinc per day. A skin or hoof problem is by no means automatic proof of a feeding deficiency.

In stables and forums, zinc supplements are often reached for prematurely when skin changes or brittle hoof horn appear. As an essential trace element, zinc is a component of more than 300 metalloenzymes and is well studied in human dermatology. However, an isolated blood value says little without a full analysis of the total ration. Un-targeted administration of high-dose zinc preparations through feed can disturb the delicate interplay of the other trace elements. If a deficiency is suspected, the vet should therefore always be consulted to balance the total ration properly.

• Daily requirement: Around 400 mg of zinc per day covers the maintenance requirement of a 500 kg horse.
• Enzymatic function: As a cofactor, zinc supports internal metabolic processes as well as horn and skin growth.
• Diagnostics before supplementing: Skin and hoof problems call for professional assessment rather than blanket supplementation.

The other route: storing the ionic form instead of creating it

The other route is not to create the ionic form on the skin first, but to supply it ready-made and already stored. In equion® Hoof and Skin Gel, zinc ions and silver ions are stored in an inert carrier material, already in their active ionic form. On contact with moisture, the ions are released in a controlled way, without any chemical bond having to break first.

Note: These explanations describe the properties of the ingredients and how the technology works. They are not statements about the healing or treatment of diseases.

In contrast to conventional zinc pastes or metallic particles, this approach removes the need for prior conversion or bond cleavage. Zinc ions take the leading role in supporting the skin barrier, while silver ions perform a complementary cleansing function. Storage in the inert carrier material ensures that release happens gradually on contact with moisture such as sweat or ambient damp. This allows an even release to be achieved, without having to overdose against an uncertain reaction. The paraffin oil based gel is deliberately low in viscosity so it can be applied in a very thin layer and remains on the surface as a light protective layer. That is precisely where its benefit lies: the gel matrix keeps the particles on the skin for as long as possible, while the ions gradually move out on contact with moisture.

• Already in ionic form: No chemical bond has to break to release the active zinc and silver ions.
• Stored in the carrier material: The inert carrier material holds the ions stable and releases them only on contact with moisture.
• Targeted use: Zinc ions support skin care, silver ions serve gentle cleansing.
• Light gel texture: Can be applied in a very thin layer and remains on the surface as a thin protective layer.

What this means for daily use

For the daily care routine in the stable, the guiding principle is to keep skin and the fetlock area clean and dry at all times and to use care products sparingly. A thin application makes it possible to check the skin's condition every day. As soon as skin areas weep, are severely swollen or the horse shows lameness, the vet must be consulted immediately.

Regardless of which care product is chosen, the affected area of skin should be gently cleansed of dirt and thoroughly dried before application. Thinly applied layers of care product protect the surface without thick crusts of dirt accumulating. In this way, minor scrapes, scratches or grazes on the skin surface can be kept clean and protected. For deep cracks, open wounds or persistent skin changes, pure care products reach their limits; here the expertise of a vet or farrier is needed.

• Prepare the skin: Gently cleanse the area of skin and let it dry completely before applying.
• Apply thinly: A very thin layer is enough to provide protection and minimise dirt adhesion.
• Daily checks: Inspect the cared-for area of skin every day for changes, heat or swelling.
• Call the vet: Seek veterinary advice immediately in case of deep wounds, weeping areas, severe swelling or lameness.