What the science says about heat, hydration, motion sickness vs anxiety

Summer travel is part of life for many dog owners in South Africa, from holiday road trips to weekend visits, and family gatherings. Yet heat remains one of the most underestimated risks dogs face during transport, particularly in vehicles.

Understanding how dogs regulate body temperature, how hydration really works, and how stress presents during travel allows owners to make informed, welfare-led decisions, including when not to travel at all.

Heat stress

Dogs don’t cool down like we do

Dogs rely primarily on panting to dissipate heat. Unlike humans, they have limited sweat glands, and their ability to offload excess body heat depends on a complex interplay of factors: airflow, ambient temperature, humidity, respiratory efficiency, and individual characteristics like body size, coat type, and breed.

In a vehicle, even one with air conditioning, these systems are compromised. The dog who seems perfectly comfortable at home may struggle in the back seat of a moving car, where conditions are fundamentally different from what their thermoregulatory system evolved to handle.

Why vehicles are risky environments

Heat builds quickly in vehicles, even with windows opened slightly. The greenhouse effect means that internal temperatures can rise dangerously within minutes, and airflow is often uneven, with the front of the vehicle receiving most of the cooling while the back remains stuffy and hot. Sun exposure through glass increases radiant heat, turning even a well-ventilated car into a heat trap.

Dogs lying on seats or in crates retain heat beneath them, unable to dissipate warmth through their undersides. Studies have shown that internal car temperatures can rise to dangerous levels faster than most owners anticipate, and dogs can overheat before anyone realises there’s a problem. The risk isn’t just when the car is stationary as moving vehicles create their own thermal challenges that catch many owners off guard.

Thermoregulation

A dog’s normal body temperature ranges from 38–39°C. Heat-related illness can begin when body temperature exceeds 40°C, and damage escalates rapidly beyond this point. What makes heat stress particularly treacherous is how quickly it can progress and how deceptive the early signs can be.

Early signs of heat stress include excessive panting, drooling, restlessness, reluctance to lie down, and glassy eyes. These symptoms are easy to mistake for normal travel behaviour, especially in dogs who are naturally anxious in cars. As heat stress progresses, dogs may show vomiting or diarrhoea, weakness or collapse, disorientation, and in severe cases, seizures.

Importantly, heat stroke can occur without obvious warning, especially during travel when other stressors are present. A dog might seem fine one moment and critical the next. This unpredictability is why prevention is so much more important than response.

Cooling strategies that work

Effective summer travel management includes travelling during early morning or late evening when temperatures are lower, pre-cooling the vehicle before loading the dog so they’re not climbing into an already hot space, and ensuring airflow reaches the dog’s area, not just the driver’s seat.

Using light-coloured bedding reduces heat absorption, avoiding direct sunlight through windows protects dogs from radiant heat, and stopping regularly for rest and hydration gives dogs a chance to recover. Never leave a dog unattended in a vehicle, even briefly. ‘Just five minutes’ is enough to cause serious damage.

Cooling mats and damp towels can help, but they are supportive tools, not guarantees of safety. They work best as part of a comprehensive approach that addresses all the factors that contribute to heat stress.

Understanding hydration and travel

The internet is full of conflicting advice about hydration during travel, and separating fact from fiction matters when your dog’s wellbeing is at stake.

The idea that ice water causes shock is largely a myth. Cool water can help lower body temperature, but forcing a dog to drink large volumes is not advised and can be dangerous. Best practice involves offering small amounts of cool (not freezing) water frequently, allowing voluntary drinking, and avoiding pouring water into the mouth of a panting dog. A panting dog has an open airway that makes aspiration (taking liquid into the lungs) a real risk.

Electrolytes are often overused in dogs, sometimes with the best intentions but without scientific backing. Electrolyte supplementation is not routinely necessary for travel and may actually disrupt sodium balance, worsen dehydration if improperly diluted, or irritate the gastrointestinal tract. Electrolytes should only be used under veterinary guidance, in dogs with documented fluid loss (such as from vomiting or diarrhoea), or for specific medical indications.

For most dogs, fresh water combined with rest and cooling is safer and sufficient. The drive to ‘do something’ can sometimes lead us to interventions that complicate rather than help.

Motion sickness vs travel anxiety

Not all ‘car stress’ is the same, and treating the wrong issue can worsen the problem. This is where careful observation becomes crucial.

Motion sickness is more common in puppies and young dogs, particularly those with immature vestibular systems (the balance system found in the dogs’ ears). Signs include drooling, nausea, vomiting, and reluctance to enter the vehicle. Motion sickness often improves with age and gradual exposure, as the inner ear matures and the dog becomes accustomed to the sensation of movement.

Travel anxiety, by contrast, is behavioural in origin and often linked to previous negative experiences, confinement stress, or anticipation of unpleasant destinations like vet visits. Signs include panting before the car even moves, pacing or trembling, vocalisation, and refusal to settle. A dog with travel anxiety may be distressed the moment they see the car keys, long before any physical motion occurs.

Understanding which issue your dog faces shapes how you help them. Motion sickness responds to anti-nausea medications and time, while anxiety requires behavioural modification and sometimes anxiolytic support.

When medication is appropriate

Anti-nausea medications may be appropriate for true motion sickness, while anxiolytic or sedative medications may help dogs with significant travel anxiety. However, medication should always be prescribed by a veterinarian, trialled before long journeys to ensure it works as intended and doesn’t cause adverse effects, and used as part of a broader management plan rather than a standalone solution.

Medication isn’t a substitute for good management. It’s a tool that works best when combined with appropriate travel conditions, gradual desensitisation, and realistic expectations about what your dog can handle.

When NOT to travel with your dog

Consider postponing travel if your dog is brachycephalic (short-nosed breeds like Bulldogs, Pugs, or Boxers, who struggle with heat regulation even in ideal conditions), has heart or respiratory disease that compromises their ability to cope with stress, is elderly or very young with less robust thermoregulatory systems, or is overweight, which increases heat retention and reduces cooling efficiency.

Dogs who have recently been ill, who show signs of heat intolerance in normal conditions, who have severe travel anxiety that significantly impacts their welfare, or who are recovering from surgery or injury should also stay home. In these cases, staying home may be the most responsible choice, even if it’s inconvenient.

Final thoughts

Travelling with dogs in summer isn’t inherently unsafe, but it demands planning, restraint, and honest assessment of risk. Heat stress doesn’t announce itself loudly. Hydration myths can cause harm when we act on misinformation. Behavioural distress often looks trivial when it’s actually caused by discomfort or physical illness.

Adapting plans around the dog – driving overnight, splitting journeys into shorter trips, or deciding not to travel – may be necessary. These adjustments reflect informed risk assessment rather than overprotection.