When your dog is taken to the vet, it is common for your pet to have their temperature checked. This is an important part of the clinical examination. Your vet will wish to find out if your pet’s temperature is within the normal range, or if it is too high or too low. Any method used to check a dog’s temperature should ideally be accurate, quick and comfortable for the animal. These factors will also make the procedure easier and safer for the vet or nurse performing the task; since the dog is less likely to wriggle or bite! So why do vets choose the “up the bottom” option?
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The most common way to take a dog’s temperature is to place a rectal thermometer into their bottom. And keep it gently in place until their temperature can be read accurately. Many thermometers are now digital and can give a reliable reading reasonably quickly. In general, the procedure is accurate and fairly quick. But many dogs seem to object to having their temperature taken with a rectal thermometer. So it may not be entirely comfortable. It is also obviously a mildly invasive procedure.
So are other methods for checking a dog’s temperature available and how do they compare to rectal thermometers?
Ear thermometers are available for dogs which use an infrared sensor to measure the temperature at the tympanic membrane (eardrum). This method can be fairly accurate because the eardrum is well within the body and not an external, or surface point. The devices are also usually fairly quick to give a reading once correctly placed. So ear thermometers can be assumed to generally meet two of the criteria for a good method of checking the temperature of a dog.
However ear thermometers are often not comfortable for the dog and this can be a major disadvantage. Many dogs resent having their ears touched or examined in any way. If they have a history of ear infections or other problems with their ears the placement of the ear thermometer may result in considerable discomfort. Since the ear thermometer must be correctly placed to record an accurate temperature a wriggling or uncomfortable patient may also mean that the temperature reading is inaccurate. And placing the probe in the right spot is harder in dogs (who have a double-right angle bend in their ear canal) than it is in humans.
As a result, for most dogs, a rectal thermometer is better tolerated than an ear thermometer. And the results are more reliable in a real-world setting.
Non contact infrared thermometers
Infrared thermometers which can read your dog’s temperature without touching your pet are an interesting method of checking an animal’s temperature. It is obviously non-invasive and many dogs tolerate it well. These devices usually meet the criteria of being comfortable for your pet. They are also fairly quick to provide a reading but are they accurate?
These devices are often used to check the temperature of a pet when aimed at the skin. Since dogs have different coat characteristics of colour, length and density of hair this can affect the ability of the thermometer to give an accurate reading. If non-haired areas are chosen this usually involves some contact with the pet. And possibly the need to change the position of the dog’s body. For example to obtain a reading from the inner thigh which usually has less hair; dogs may resent this.
To get around the problem of the hair coat causing inaccuracies some studies have used corneal temperatures. However some dogs resent the device being directed into their eyes. The readings do not correlate particularly well to rectal temperatures; which are a fairly reliable indicator of a pet’s core body temperature. So the readings provided by these thermometers may be an inaccurate indicator of core body temperature. And that makes sense. After all, dogs are descended from wolves, who are well evolved to keep heat in and not out (where it can be sensed by the infrared device!).
Microchips which can detect a dog’s temperature are available. But they are generally more expensive than the normal microchips which are used solely for identification purposes. They work in the same way as a normal microchip except that they show your pet’s temperature in addition to their unique microchip number when a scanner is passed over the microchip.
Dogs do not seem to resent having their microchip scanned and since most microchips are placed between the dog’s shoulder blades they may not even realise that the vet is doing anything at all. This can be helpful if your pet is particularly nervous. However, the microchip measures the temperature of the subcutaneous tissue in which it is placed and may not always reflect the dog’s core body temperature as reliably as a rectal thermometer. So if your pet is unwell, or your vet is concerned in any way they may wish to check your pet’s temperature rectally as usual.
Pet owners often touch their dog’s nose to find out if it is cool and moist or warm and dry. Sadly, this is an unreliable method of checking your pet’s temperature. A dog’s nose may be warm and dry for many reasons and dogs which are unwell can still have a cool wet nose.
Interestingly the myth surrounding the condition of a dog’s nose as a basis of checking their health may have a historical basis originating from a time when distemper was a common disease in dogs. Dogs with this condition would develop thickened tissue on their nose (a condition known as hyperkeratosis). This would have resulted in their nose feeling warm and dry rather than cool and wet. Luckily, vaccination prevents this disease and it is uncommon to find a dog with distemper now. These days the temperature and moisture of your pet’s nose is unlikely to be a significant sign of anything at all.
Some pet owners like to examine the temperature of their dog’s ears and other body areas. Again, this method of checking an animal’s temperature is extremely unreliable. Any excessive heat in the area being palpated may simply be due to localised inflammation and should not be considered to be a method of checking your pet’s true body temperature.
So which type of thermometer is the best?
Although several different methods of checking a dog’s temperature are available, the rectal thermometer is usually the best device overall in terms of accuracy, speed and being relatively well tolerated by the patient. This is the reason for them being so widely used in veterinary practices to check dog’s temperatures. While in the future better alternative devices may be available, for the moment, this is the best option we have.