The Study of Cannabis For Horses

The Study of Cannabis For Horses

Cannabis is a complex plant containing hundreds of naturally occurring compounds, but the two most well-known are THC (tetrahydrocannabinol) and CBD (cannabidiol). These compounds interact with a biological network that already exists in the body called the endocannabinoid system (ECS).

Understanding the ECS helps explain why cannabis-based topicals may help some people or perhaps, animals, with localized discomfort.

What is the Endocannabinoid System?

The endocannabinoid system (ECS) is a cell-signaling system found throughout the body. Its job is to help maintain homeostasis, or internal balance. It plays a role in regulating:

  • Pain perception
  • Inflammation
  • Mood
  • Sleep
  • Immune function
  • Appetite
  • Memory
  • Skin health

The ECS works through three main parts:

1. Endocannabinoids

These are cannabinoids that your body naturally produces, including:

  • Anandamide ("the bliss molecule")
  • 2-AG (2-arachidonoylglycerol)

Your body makes them as needed rather than storing them.

2. Cannabinoid Receptors

These receptors act like locks that cannabinoids can interact with.

CB1 receptors

  • Primarily found in the brain and central nervous system.
  • Influence pain, memory, movement, mood, and appetite.
  • Responsible for the intoxicating effects of THC when it reaches the brain.

CB2 receptors

  • Found mainly on immune cells and in peripheral tissues.
  • Also present in skin, joints, muscles, connective tissue, and peripheral nerves.
  • More closely associated with inflammation and immune responses.

3. Enzymes

These enzymes break down endocannabinoids once they've done their job.

How THC Works

THC is unique because it can bind strongly to CB1 receptors.

When THC is inhaled or eaten, it enters the bloodstream and eventually reaches the brain, where it activates CB1 receptors. This can produce effects such as:

  • Euphoria
  • Altered perception
  • Relaxation
  • Increased appetite
  • Reduced pain perception
  • Changes in short-term memory and coordination

THC can also activate CB2 receptors, which may contribute to anti-inflammatory effects.

How THC Topicals Work

A THC topical (cream, balm, lotion, or salve) works differently from inhaled or edible cannabis.

When applied to the skin:

  • THC interacts primarily with cannabinoid receptors in the skin and nearby tissues.
  • It may also influence receptors involved in pain signaling, such as TRPV1 receptors, which are associated with heat and pain sensation.
  • Very little THC is typically absorbed into the bloodstream when used as intended on intact skin.

Because of this:

  • Most THC topicals do not produce a psychoactive "high."
  • Instead, their effects are generally localized to the area where they are applied.

Why Might THC Topicals Help Comfort Pain?

Research is still developing, but scientists think several mechanisms may be involved.

1. Modulating Pain Signals

Activation of cannabinoid receptors may reduce the sensitivity of local pain pathways, making discomfort feel less intense.

2. Supporting the Body's Inflammatory Response

Inflammation is a normal part of healing, but excessive or chronic inflammation can contribute to discomfort.

CB2 receptor activation may influence immune-cell activity and inflammatory signaling, potentially reducing inflammatory processes in the treated area.

3. Relaxing Surrounding Tissue

Many users report relief in sore muscles and stiff joints after applying cannabinoid topicals. Some of this effect may come from cannabinoid signaling, while ingredients commonly added to balms (such as menthol or essential oils) can also contribute.

4. Localized Action

Because the cannabinoids remain largely in the tissues beneath the application site, people often use topicals for:

  • Arthritic joints
  • Muscle soreness
  • Tendon discomfort
  • Back pain
  • Neck pain
  • Minor sprains
  • Overworked hands or knees

Why Doesn't a THC Balm cause psychological effects?

The skin is an excellent protective barrier.

Standard THC creams and balms generally do not deliver enough THC into the bloodstream to cause intoxication when applied to intact skin. Instead, they primarily act on receptors located in the skin and nearby tissues.

This is different from transdermal cannabis patches, which are specifically engineered to deliver cannabinoids through the skin into the bloodstream. Those products can have systemic effects.

What This Means for Animals

Many mammals—including horses, dogs, and cats—also have an endocannabinoid system. Researchers have identified cannabinoid receptors in multiple animal species, making this an active area of veterinary research.

it's accurate to say that the biology exists and research is emerging, while also acknowledging that the evidence base in horses is still developing.

1. Studies proving animals have an Endocannabinoid System (Strong Evidence)

This is no longer debated.

Researchers have identified cannabinoid receptors throughout many animal species, including:

  • Horses
  • Dogs
  • Cats
  • Cattle
  • Rodents
  • Primates

These receptors are found in the:

  • Skin
  • Nervous system
  • Immune cells
  • Joints
  • Muscles
  • Digestive tract
  • Brain (species-dependent)

This means animals possess the biological machinery needed to respond to cannabinoids, although the response varies by species. 

2. Studies Mapping Cannabinoid Receptors

Researchers have spent years identifying where CB1 and CB2 receptors exist.

For horses, studies have identified receptors in:

  • Skin
  • Peripheral nerves
  • Joint tissues
  • Immune cells
  • Musculoskeletal tissues

This is important because topical creams act locally.

If receptors are present in these tissues, could cannabinoids influence pain and inflammation?

3. Veterinary Clinical Studies (Mostly Dogs)

Researchers have conducted:

Osteoarthritis trials

Several randomized, placebo-controlled clinical trials evaluated CBD-dominant formulations in dogs with osteoarthritis.

Reported findings included:

  • lower pain scores
  • improved mobility
  • increased activity
  • improved quality of life

These studies were generally well tolerated, although formulations, doses, and study quality varied.

Epilepsy

Clinical studies have evaluated CBD as an add-on therapy in dogs with epilepsy.

Some trials found reductions in seizure frequency for certain dogs. 

Skin Conditions

Researchers have also begun studying cannabinoids for:

  • itching
  • allergic skin disease
  • inflammatory skin disorders

Because the skin contains cannabinoid receptors, this is an active area of investigation.

4. Horse Research

Published work has included:

Pharmacokinetic studies

Researchers have measured:

  • how CBD is absorbed
  • blood concentrations
  • metabolism
  • elimination

These studies help determine safe dosing but do not prove efficacy.

Safety studies

Researchers have monitored:

  • heart rate
  • blood chemistry
  • liver values
  • behavior
  • adverse effects

to better understand tolerability.

Pain and Sensitivity

There are only a handful of clinical reports.

One published case described a horse with severe sensitivity to touch that improved while receiving oral CBD after conventional therapies had not resolved the problem. Because it was a single case, it cannot establish that CBD caused the improvement, but it can help generate hypotheses for future studies.

Topical THC Research in Horses

This is where things become exciting—but also where you need to be careful.

As of now:

  • There are very few published controlled studies evaluating THC topical creams in horses.
  • There is no strong body of evidence showing that THC topical balms relieve equine arthritis or musculoskeletal pain.
  • This represents a genuine research gap rather than proof that they work or do not work.

My Message

We already know horses have an endocannabinoid system and cannabinoid receptors throughout their bodies. We've seen promising veterinary research in other species and growing evidence in horses, yet topical cannabinoids for equine pain remain largely understudied. I'd like to see more research exploring whether these products could safely improve comfort and quality of life.

 

  • Di Salvo et al. (2024) – Endocannabinoid System and Phytocannabinoids in the Main Species of Veterinary Interest: A Comparative Review
    This is one of the most comprehensive reviews available. It summarizes receptor locations, pharmacology, and studies across dogs, cats, horses, and livestock.
  • Gamble et al. (2018) – Randomized placebo-controlled trial of CBD for canine osteoarthritis, one of the foundational veterinary cannabinoid studies. It reported improvements in pain and activity in dogs receiving CBD compared with placebo.
  • Brioschi et al. (2020) – Clinical study of CBD for osteoarthritis in dogs, adding to the evidence that cannabinoids may help some canine patients with chronic pain.