The oldest small idea in the Americas.

01Origins: a dog of the ancient Americas

Long before anyone called it a Chihuahua, a small, quiet companion dog lived alongside the peoples of central Mexico. Spanish writers of the colonial period described a little dog known as the techichi, and historians link it to the Toltec civilisation, whose influence spread across central Mexico from around the tenth century. When the Aztecs rose to power, the small dog appears in their world too: in households, in religious life and, uncomfortably for modern readers, sometimes as food or as a sacrifice intended to guide the dead.

Pottery from western Mexico, particularly the famous dog effigies of Colima made roughly two thousand years ago, shows how central dogs were to life in the region. Those figures are plump, short-legged dogs rather than Chihuahuas, but they belong to the same long story of small dogs bred close to people.

Here the honest version gets more interesting. Genetic research on ancient and modern dogs has found that the dogs living in the Americas before European contact were almost entirely replaced by European breeds after the sixteenth century. Studies of modern Chihuahuas have found that they carry a small trace of that older, pre-contact ancestry, more than most breeds but far from all of it.1 So the Chihuahua is best understood as an ancient idea that was revived and reshaped in the nineteenth and twentieth centuries, rather than an unbroken line from Aztec palaces.

02From Chihuahua to Britain

The breed takes its name from the state of Chihuahua in northern Mexico, where American travellers and traders in the mid-nineteenth century came across very small dogs for sale. Breeders in the United States began to standardise the type, and the American Kennel Club recorded its first Chihuahua in 1904.2

The breed reached Britain in the early twentieth century and became established after the Second World War. Today the Royal Kennel Club (the Kennel Club received its royal title in 2023) lists two breeds in its Toy Group: the Chihuahua (Smooth Coat) and the Chihuahua (Long Coat). They share a breed standard apart from coat, and registered dogs of one coat aren’t bred with the other.3

03Apple head and deer head

These are the two phrases new owners hear most, and they’re often explained badly.

The apple head is the shape the breed standard asks for: a well-rounded, “apple dome” skull, a short, slightly pointed muzzle, a clear stop where the forehead meets the muzzle, and large, round eyes set well apart. Ears are large, flared and carried upright when alert.3

Deer head is an informal term for a Chihuahua with a flatter, longer skull, a longer muzzle and a gentler slope from forehead to nose. These dogs often look leggier. The term isn’t in the breed standard, so deer-head dogs aren’t shown, but they are common as pets and in rescue. A deer-head Chihuahua is not a different breed, and it isn’t less of a Chihuahua.

The soft spot: molera

Many Chihuahuas are born with a molera, a soft spot on the top of the skull where the bones haven’t fully joined, much like a human baby’s fontanelle. In many dogs it closes or shrinks as they grow; in some it stays open for life. An open molera isn’t a disease in itself, but it means that part of the skull needs protecting: no tapping on the head, care with doorways and toys, and a vet check if the head looks unusually domed or the dog seems dull, wobbly or has seizures, since those can be signs of hydrocephalus (fluid on the brain), which is more common in toy breeds.

“Teacup”, “micro” and “mini”

These words describe a sales strategy, not a type. There is no teacup Chihuahua in the breed standard. Breeding for extreme smallness increases the risk of low blood sugar in puppies, fractures, dental crowding, hydrocephalus and difficult births. A seller who leads with “teacup” is telling you something about their priorities. See warning signs when buying.

04Size, coat and colour

The UK breed standard asks for a dog weighing up to 2.7 kg (6 lb), with 1–1.8 kg (2–4 lb) preferred. In practice, many healthy pet Chihuahuas are heavier than that, especially longer-legged dogs, and that’s fine if they are lean. What matters for your dog is their body condition score, not a number on the scale.

The UK standard accepts most colours and combinations, from fawn, cream and red to chocolate, black-and-tan and tricolour. Merle needs a special word. The merle gene produces a mottled coat and, when two merle dogs are bred together, a high risk of deafness and eye defects in the puppies. The Royal Kennel Club does not register merle Chihuahuas, and responsible breeders avoid producing them. A litter advertised as “rare merle” is a warning sign.3

Chihuahuas are not hypoallergenic. No dog is, and both coats shed. People with dog allergies sometimes cope better with a small dog simply because there is less dog, but that’s worth testing by spending real time with Chihuahuas before committing.

05Lifespan: longer than the averages suggest

The largest UK study of Chihuahua health looked at the veterinary records of more than 11,000 Chihuahuas seen at primary-care practices through the VetCompass programme at the Royal Veterinary College. Among dogs that died during the study, the average age at death was 8.2 years: 10.2 years for females and 6.9 for males.4

That figure is lower than the 12 to 20 years often quoted online, and it deserves careful reading. It reflects the dogs that died during the study period, including young dogs killed in accidents. The three most common recorded causes of death were heart disease (18.8%), lower respiratory tract disorders (16.3%) and traumatic injury (13.8%).4 Trauma is the one you can most influence: falls from arms and furniture, being stepped on, car accidents and attacks by larger dogs. Plenty of well-cared-for Chihuahuas live well into their teens, so plan for that.

A long life with a Chihuahua is common. It is also something you have to build, especially in the first two years.The editors

06Temperament: alert, devoted and opinionated

People who live with Chihuahuas describe the same cluster of traits: intensely loyal, alert to every sound, brave out of proportion to their size, and fond of warmth, laps and burrowing under blankets. Many bond most closely with one person while remaining friendly with the rest of the household.

The traits that make them charming can make them hard work. A dog that notices everything will often announce everything, so Chihuahuas can be vocal. A dog that is small and easily hurt can learn that the world is frightening, and fear in a small dog often looks like aggression: growling, snapping or lunging at hands, strangers or bigger dogs. In the VetCompass study, aggression was recorded more often in Chihuahuas than in other breeds, and more often in males than females.4

Read that as a reason to invest in early, gentle socialisation, not as a fixed fact about the breed. Most so-called “small dog syndrome” is learned. A dog that is constantly picked up, carried past things it finds scary and never allowed to approach the world at its own pace has little chance to build confidence. A dog that is given choices, rewarded for curiosity and protected from being overwhelmed usually grows into a stable, sociable companion. Our behaviour guide explains how.

07Every dog is different

Breed tells you what is likely, not what you will get. Personality in dogs is shaped by genetics, the mother’s health and stress during pregnancy, the first weeks with the litter, and everything since. Two puppies from the same litter can differ as much as two siblings in any family.

When you meet a Chihuahua, whether a puppy or a rescue adult, watch for these five things. None is good or bad in itself; they tell you what kind of home and training will suit that dog.

08Myths, corrected

“They shake because they’re nervous.”

Sometimes. Chihuahuas also shiver because they’re cold (they lose heat fast), because they’re excited, because they’re in pain, or because their blood sugar is low, which can be dangerous in puppies. Shivering with weakness, wobbliness or dullness needs a vet. See urgent signs.

“They don’t need walks.”

They need less distance than a spaniel, not less life. Short daily walks give them exercise, mental stimulation and the confidence that comes from exploring on their own feet.

“Small dogs don’t need training.”

Untrained behaviour in a small dog is easier to tolerate, so it often goes unaddressed. Chihuahuas are clever and very trainable with reward-based methods, and training is good for their confidence.

“They’re fine in a handbag.”

Being carried everywhere denies a dog exercise and the chance to learn about the world, and a dog in a bag can’t move away from things it fears. Carry them when it keeps them safe, such as in crowds, on escalators or near unfamiliar large dogs, and let them walk the rest of the time.