Healing animals are not just a pretty metaphor, but rather a reality that science and everyday experience confirm time and again. From the dog that greets you with a wagging tail after a terrible day, to the chimpanzee that chews a medicinal plant to rid itself of parasites, the animal kingdom is full of surprising strategies for protecting its own health and that of others.
In recent years, interest in understanding how animals influence human health has skyrocketed.and also how they protect themselves against diseases, parasites, stress, or pain. Therapies assisted by dogs, horses, or cats coexist with studies on cancer-resistant naked mole rats, fish capable of tolerating extremely high glucose levels, or butterflies that "medicate" their offspring before birth. All of this paints a fascinating picture where the line between human and animal medicine becomes very thin.
Animals that heal people: affection, emotional support and therapy
Anyone who has gone through a difficult time in life and had a pet by their side He knows that this support is no small thing. A dog or a cat doesn't judge, doesn't reproach, doesn't demand explanations; they are simply there, they accompany, they offer physical contact and a stable presence that is often lacking in human relationships. This unconditional acceptance awakens in the person a sense of security and comfort that is difficult to find elsewhere.
A study by a veterinary pharmaceutical company indicated that more than half of pet owners in Spain They considered their pet's affection to be key in overcoming very difficult times, such as the loss of a loved one or a breakup. If the focus is broadened to include work conflicts, family arguments, or periods of low self-esteem, the percentage of those who point to their pet as a fundamental support skyrockets to almost 100%.
This protective effect is not limited to the emotional aspect, but it has become the basis of multiple structured interventions: the so-called animal-assisted activities (AAA) and zootherapy or animal-assisted therapy. Dogs, cats, and other animals are used in nursing homes, day centers, hospitals, and psychology clinics. feline therapyhorses, rabbits and even other animals to promote communication, reduce stress and improve the mood of people who are going through a difficult time.
In therapeutic contexts, the presence of the animal acts as a bridge between the professional and the patient. People with depression, anxiety disorders, relationship difficulties, autism, or intellectual disabilities often open more easily When there is an animal in the room: they talk about it, they pet it, they relax and, almost without realizing it, they also begin to talk about themselves and what hurts them.
The effects are not only psychological: physical benefits have also been measured. associated with contact with animals. Spending time with a pet, petting it, or playing with it is linked to lower blood pressure, improved heart rate, the release of endorphins, and a reduction in stress hormones like cortisol. In other words, the body enters a calmer state, more conducive to recovery.
Dogs, cats, horses, and other animal-assisted therapy companions
Although almost any animal could theoretically be used for assisted intervention, In practice, breeds and species with a particularly sociable, predictable, and easy-to-manage temperament are often chosen. In the case of dogs, Labradors, Golden Retrievers, Newfoundlands, and Belgian Shepherds, among others, are very common due to their learning ability, patience, and friendly nature.
Specific individuals and breeds are also selected with cats.Like Siamese cats or other particularly affectionate and well-balanced felines, these cats tolerate physical contact and changes in environment well. They are not just any shy or withdrawn cat, but animals carefully evaluated to ensure they enjoy interaction and do not suffer from it.
Rabbits, such as Mini Rex, Dutch or Daisy, and Arabian or Spanish horses They have also been successfully incorporated into numerous programs. In the case of horses, equine therapy has proven especially useful for people with mobility problems, cerebral palsy, developmental disorders, or neurological sequelae, since the horse's movement stimulates muscles and balance, while also offering a powerful emotional stimulus.
One interesting detail is that animal-assisted therapists often choose the shyest animal in the litter.Far from the stereotype of the "more outgoing" puppy, this somewhat more reserved, yet stable, character usually translates into reliable animals, attentive to human signals and easier to integrate into therapeutic dynamics where calm and security prevail.
Where does the therapeutic power of these animals lie? In large part, it's due to their lack of prejudice. The animal doesn't question the patient's appearance, past, disability, or mistakes. For them, the person is simply someone to connect with. This acceptance allows the patient to gradually let go of self-defense and look outward, toward the animal, awakening empathy and self-love through the bond.
A reciprocal relationship: responsibility and limits of animal-assisted therapy
Clinical psychology specialists who work with animals always remember one key idea: The animal is not a doctor, a psychologist, or a miracle pill. It is a facilitator, a support, a companion in the process. Its presence can open inner doors that would otherwise be much more difficult to access, but always within a framework of professional therapy and... ethical responsibility towards the animal itself.
Thinking "I'm sad, I'll buy a dog and everything will be fixed" is a serious mistakeCaring for a dog or cat involves a long-term commitment: around 15 years on average, with emotional, financial, and time demands that must be met. In the case of longer-lived animals, such as some parrots, the responsibility can last for practically a human lifetime.
When this relationship is understood as a reciprocal bond, and not as a simple resource for personal use, The results can border on what many describe as miraculous. There are documented cases of people with deep depression, devastating grief, or traumatic separations who, thanks to a zootherapy program, have managed to redirect their lives by relying on their relationship with a horse, dog, or cat with whom they have connected very intensely.
A striking example is that of a woman with severe depression following a marital breakup.who reached a point of extreme despair. In the context of mare-assisted therapy, the bond she formed with this animal allowed her to confront her pain in a different way, regain self-esteem, and feel confident about the future again. Years later, she still remembered that mare as a friend to whom she owed part of her recovery.
From a physiological point of view, contact with animals in therapy reinforces and enhances the psychological effects.Improvements have been observed in sleep patterns, blood pressure regulation, and a reduction in anxiety-related tachycardia, as well as a greater willingness among patients to move, leave the house, and establish healthy routines. All of this contributes to a more balanced life.
The animal world as a natural laboratory of medicine
Beyond emotional care, animals are also an immense source of biomedical knowledgeComparing how different species get sick, or don't get sick, has allowed us to discover invaluable clues about serious human pathologies such as cancer, cardiovascular diseases, diabetes, or joint problems.
Our DNA is very similar to that of other mammals, especially chimpanzees, But small differences can be decisive. In some cases, they have made us more vulnerable, and in others, seemingly humble species have developed resistance mechanisms that are now being studied closely in the hope of translating them into new therapies.
Genetic engineering and tools like CRISPR have opened the door to the possibility, still distant but real, of correcting certain human vulnerabilities by drawing inspiration from what we see in other animals, including examples of transgenic animalsAlthough there is still a long ethical and technical road ahead, the idea of "learning from animals to edit our diseases" is already part of the current scientific debate.
Chimpanzees and cardiovascular disease: a matter of genes and lifestyle
As the human species has evolved, some changes have occurred in our genetic makeup. These factors have made us more prone to developing arterial blockages, with a consequent increase in the risk of heart attack or stroke. If we add to that dietary changes (more red meat, saturated fats, processed foods) and sedentary lifestyles, the perfect recipe for a surge in cardiovascular disease.
Recent research has identified the loss of a specific gene in humans This gene distinguishes us from other animals, including our close relative, the chimpanzee. This genetic loss is associated with a significant increase in the risk of coronary problems, something not observed with the same intensity in chimpanzees or other species that retain this gene.
To test this, laboratory mice were modified by introducing the same mutation into them. that we humans suffer from, and the result was striking: these mice had twice the risk of heart attacks compared to the unmodified mice. This suggests that part of our cardiac vulnerability is not only due to poor diet and exercise, but also to our own biology.
Looking ahead, it is possible that genetic engineering could help reduce this disadvantage. This allows us to design more specific treatments based on a very precise understanding of which genes are involved and how they interact with diet and the environment. Meanwhile, studying chimpanzees and other animals less prone to these types of illnesses provides us with clues for better prevention in humans.
Naked mole rats: the mystery of an animal almost immune to cancer
The naked mole rat, with its wrinkled and unflattering appearance, It has become a true star of science. These subterranean rodents exhibit an absolutely extraordinary characteristic: they practically do not develop cancer, despite living many years longer than would be expected for an animal of their size.
While other similar rodents typically live for around four years, Naked mole rats can easily live seven times longer. This extra lifespan is also accompanied by a very high resistance to malignant tumors, which has sparked enormous interest in understanding the underlying cellular and molecular mechanisms.
Among the hypotheses being considered are improved immune surveillance, They possess tissues that are especially resistant to uncontrolled cell proliferation, and highly efficient DNA repair systems. Little by little, laboratory experiments are revealing how these rats manage to sustain such a long lifespan without succumbing en masse to cancer.
Although we are still far from directly transferring these characteristics to humans, The knowledge derived from their study is already inspiring new lines of research against tumors and age-related diseases, with the aim of improving both the quantity and quality of years lived and boosting the medicine of tomorrow.
Kangaroos and osteoarthritis: joints that withstand the jump
Osteoarthritis, that painful wear and tear of the joints that so many people suffer from, It has multiple causes: excess weight, poor posture, mechanical overload, muscle imbalances, among others. It is not exclusive to humans; many mammals, including great apes and carnivores, also frequently suffer from it.
However, kangaroos, which spend their lives making high-intensity hops, They seem to largely escape this fate. They can reach speeds close to 60-65 km/h while jumping, and maintain this activity into old age with a surprisingly low level of joint damage considering the load their knees bear.
The key lies in a very particular cartilaginous structure in their knees.The cartilage cushions and distributes impact very efficiently, and the arrangement of its ligaments provides great stability to the joint. This combination protects the cartilage from excessive wear, even under repeated stress.
Understanding in detail how those kangaroo knees are built and how they work It can help design better knee prostheses for humans and stronger materials for joint implants, reducing the failure rate and improving the mobility of millions of people with joint wear and tear problems.
Blind cavefish: clues to understanding diabetes
Diabetes is one of the major global health challenges, with nearly one in ten adults affected and serious consequences such as blindness, kidney failure, cardiovascular problems, stroke, or amputations. Blood glucose control is key, but it is also extremely complex.
In this context, a small fish from Mexican caves has caught the attention of researchers, Because it has developed an extreme strategy to survive in environments where food is scarce for long periods. This fish, accustomed to gorging itself when it finds food, can withstand extremely marked variations in its sugar levels without suffering the typical damage we would see in a diabetic human.
Adapted to an environment with long periods of fasting and brief opportunities to eat a lot, It has evolved to tolerate glucose levels that, in a human, would be clearly pathological. It does not exhibit the same degree of vascular, neurological, or organ damage that human medicine would expect under those circumstances.
To study its regulatory and protective mechanisms against excess glucose This could open the door to more effective and less aggressive treatments for diabetes, perhaps inspiring drugs that mimic some of these peculiar biological adaptations.
Zebras, stress and ulcers: how lifestyle impacts the stomach
We live in an increasingly stressful society, where many people spend years enduring work pressure, financial worries, mental strain, and relentless emotional problems. This chronic stress not only affects mood but also has very real effects on the body, including the development of gastrointestinal ulcers.
Wild animals, such as zebras, usually experience stress in a different way, linked to specific and momentary dangers: fleeing a predator, finding water or food, avoiding a fight. These are intense peaks of tension, but they do not last indefinitely; when the threat passes, their body returns to a baseline state of calm.
This difference in pattern explains why constant human stress It is so clearly associated with the development of ulcers, while many wild animals do not suffer from them to the same extent. However, when laboratory animals, such as rats, are exposed to prolonged and continuous stress, they also develop gastric lesions very similar to those seen in humans.
These experiments serve as a reminder that our modern lifestyle It's profoundly unnatural from the perspective of how the body is designed to manage stress. Learning from the activation and relaxation cycles of wild animals could help us design routines and environments that don't so negatively impact our digestive and overall health.
Animals that self-medicate: nature as a first-aid kit
Alongside its role as a source of inspiration for human medicine, Many animals have developed behaviors that could be described as veritable "home remedies" for treating their own ailments. This phenomenon, known as animal self-medication, is being increasingly well-documented by biologists and ethologists.
Far from being limited to "mere instinct", In many cases, a combination of physiological sensitivity, individual learning, and social observation seems to be involved. That is, animals sense that something is wrong, they test resources in their environment, and if these work, that behavior is maintained and transmitted within the group.
Self-medication behaviors have been described in primates, insects, birds, and other vertebrates. From chimpanzees that chew bitter bark to combat parasites, to butterflies that choose specific toxic plants so their future caterpillars will have fewer infections. Each species adapts its "pharmacy" to its surroundings.
The best-documented cases show repeated patterns, clearly associated with situations of illness or risk, This reinforces the idea that these are not random acts. Although we cannot know what animals are "thinking" when they self-medicate, the context and the results speak for themselves.
Chimpanzees that use medicinal plants: the case of the bitter leaf
In the 80s, in Tanzania, the observation of a sick chimpanzee named Chausiku It marked a turning point in the study of animal self-medication. Primatologist Michael Huffman noticed that the animal, exhibiting symptoms of lethargy and loss of appetite, began chewing the bark and leaves of a specific plant that was not part of its usual diet.
That plant, known as Vernonia amygdalina or “bitter leaf”, It has been used for generations by African human communities to treat malaria, fever, and intestinal parasites. What is striking is that chimpanzees rarely consume it except when they appear ill, and its extremely bitter taste makes it unappealing as a simple food.
After ingesting the bitter leaf, Chausiku showed a clear improvement in less than 24 hours. regaining activity and appetite. Subsequent analysis of stool and urine samples suggested that it probably suffered from a parasitic infection, which would have subsided thanks to the properties of the plant.
Since then, Huffman and other teams have accumulated similar observations. in different groups of chimpanzees, reinforcing the hypothesis that they use plants with medicinal compounds when needed. It is unclear to what extent they are aware of the specific effect, but it does seem evident that they have learned, directly or indirectly, that certain plants "feel good" when they are unwell.
This type of study has overturned the belief that medicine was exclusive to humans. showing a continuum between our rationalized use of drugs and the intuitive use that other species make of the plant resources available to them.
Caterpillars that change their diet to kill parasites
In the insect world we also find fascinating examples of self-medication, like the behavior observed in woolly bear caterpillars, which later transform into tiger moths. Normally, these caterpillars feed on a few specific plants, but when they are infested by certain parasitic flies, they drastically alter their diet.
Flies lay their eggs inside the caterpillar's body, And the larvae end up devouring the host from the inside. It's a virtually guaranteed fate, unless the caterpillar resorts to a high-risk strategy: starting to eat plants rich in pyrrolizidine alkaloids, substances toxic to both the parasites and the caterpillar itself.
Research by biologist Michael Singer showed that these infected caterpillars They voluntarily expand the variety of plants they consume, including species such as sagebrush, St. John's wort, and rattlesnake, all of which contain bitter and poisonous compounds. In healthy caterpillars, this diet reduces survival; in infected caterpillars, however, it significantly increases their chances of survival.
Interestingly, despite having a very simple gustatory sensory system, with only four taste buds, One of these genes seems specially adapted to detect these toxic alkaloids and trigger its preference for them when the animal is parasitized. It's as if the caterpillar's internal state "reconfigures" its sense of taste to seek out the most suitable remedy.
This phenomenon is very similar to the side effects of medications in humans: We accept certain side effects (nausea, fatigue, risk of other problems) in exchange for eliminating a more serious disease. In the case of caterpillars, the strategy sometimes works and sometimes doesn't, but it has been useful enough in evolutionary terms to persist.
Monkeys and lemurs that use millipedes as a natural repellent
In the jungles of South America and Madagascar, some primates have learned to rely on insects. to protect themselves from pests and bites. Capuchin monkeys and lemurs have been observed capturing millipedes of the genus Orthoporus dorsovittatus, biting and crushing them to extract a thick substance which they then rub all over their bodies.
This “chemical bath” ritual is performed mainly at certain times of the year where mosquitoes and other blood-sucking insects abound, suggesting that it is not a coincidence, but an adaptive response to the increased risk of bites and vector-borne diseases.
Millipedes secrete benzoquinones, toxic chemical compounds with a strong repellent effect. against many invertebrates. Applied to the fur of primates, they act as a kind of natural repellent, reducing bites and, therefore, the likelihood of infection.
Scientists cannot say for sure whether primates “know” they are using a repellent. But the correlation between millipede use and periods of peak risk indicates at least a clear connection between behavior and health protection. Perhaps the animals simply perceive it as something that "relieves" them or "makes them feel good," but the practical result is undeniable.
Chimpanzees applying insects to their wounds
Another recent discovery that has caused a sensation is the use of insects by chimpanzees. to treat open wounds. A 2022 study with chimpanzees in Gabon documented nearly twenty cases in which these primates caught insects, bit them, and then applied their crushed bodies directly to cuts or injuries.
In one of the most striking episodes, a chimpanzee named Freddy, With a recent wound on his arm, he was seen carefully capturing an insect, chewing it, and pressing it onto the injured area. He repeated the process several times, as if he were applying a natural ointment.
The most surprising thing is that this behavior was not limited to self-care: Chimpanzees were also observed catching insects and giving them to other group members to apply to each other's wounds, or even directly treating a fellow member's wound. This introduces a social and cooperative dimension to their behavior, going beyond mere individual survival.
Although it is still not clear exactly what properties those insects have. (antibiotic, anti-inflammatory, analgesic, healing properties…), the repetition of the gesture in very specific contexts points to some kind of perceived benefit. It may have also become a social custom over time, passed down from generation to generation in that chimpanzee community.
Urban birds that use cigarette butts as a parasite repellent
In urban environments, the creativity of animals to adapt to what they find This can lead to mixed strategies, with both benefits and risks. A clear example is offered by finches and city sparrows that use cigarette butts as part of their nesting material.
At first glance, it might seem like a simple consequence of the availability of human waste, But researchers from the National Autonomous University of Mexico observed that nests with more cigarette butts had significantly fewer mites, ticks, and lice than those built without these remains.
Nicotine and other compounds in tobacco have a clear insecticidal effect. And birds, indirectly, have found in cigarette butts a substitute for the aromatic plants they would use in natural environments to repel parasites. The result: chicks better protected against infestations in a city full of threats.
However, there is a downside: prolonged exposure to the toxic substances in cigarettes. It damages red blood cells and can affect both adults and chicks. Despite this, studies have found that chicks in nests with cigarette butts tended to weigh more and show better overall health, indicating that, overall, the benefit outweighs the harm in this context.
This example illustrates very well how urban animals They are reinventing their traditional medicinal resources with human materials, with results that, although not ideal, demonstrate an enormous capacity for adaptation to the environment.
Monarch butterflies: medicine for the young before they hatch
Monarch butterflies are famous for their spectacular migrations, but also because of a very fine sanitary behavior: females infected by certain parasites carefully choose the plants where they lay their eggs to protect their future caterpillars.
The parasite Ophryocystis elektroscirrha can deform the wings of young butterflies, This impairs their ability to fly and drastically reduces their chances of surviving and completing their migratory cycle. To counteract this threat, infected females show a clear preference for laying eggs on milkweed species with high levels of cardenolides, toxic compounds that inhibit the parasite's development.
Research led by biologist Jacobus De Roode demonstrated that These females changed their egg-laying pattern when parasitized, "betting" on plants that were more bitter and dangerous to many other herbivores, but beneficial to their own offspring in the context of the specific parasite they faced.
We don't know if butterflies are "aware" of being sick, But it is clear that their physiological state modifies the choice of plant host and that this change reduces the probability of infection in the next generation. In practice, it is a form of prenatal preventive medicine.
This type of behavior reinforces the idea that self-medication is deeply ingrained. In the evolutionary history of animals, appearing in lineages as diverse as insects, birds, or primates, always with the same basic logic: to take advantage of resources from the environment to minimize the impact of diseases and parasites.
An exchange of knowledge between humans and animals
The relationship between animals and diseases is not one-way, where only we learn from them. In many cases, the reverse also occurs: human medicine is applied to save and improve the lives of other species. Techniques developed to treat infections, tumors, eye problems, or reproductive disorders in people are adapted to care for wild and domestic animals.
A well-known example is the work with koalas affected by chlamydia, A bacterium that can cause sterility, blindness, and even death in these marsupials. The accumulated knowledge about chlamydia in humans has been used to design diagnostic, treatment, and prevention strategies in koala populations, attempting to curb the spread of the disease.
This constant exchange of knowledge between human and veterinary medicine It contributes to the "One Health" vision, which understands human, animal, and environmental health as components of a single system. Animals that heal, in any of the ways we have seen, remind us that living longer and better is not just a matter of technological advancements, but also of observing, respecting, and learning from the solutions that nature has been perfecting for millions of years.
