Hi this is what I found on Internet regarding ear thermometers and dogs
How To Take Your Dog’s Temperature
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When your dog is ill, it's often important to know whether or not he has a fever because it may help you decide if he needs immediate veterinary care. While you may have heard that feeling your dog's nose or ears is a good way to determine if he's feverish, it is by no means accurate. You need to get his internal temperature, and the most reliable way to do that is with a rectal thermometer.
How to use a rectal thermometer
It's not difficult to take your dog's temperature rectally, but it is a task best performed by two people. Have someone hold the dog still, preferably someone the dog knows and likes. If no help is available, make your dog lie down on his side and hold him as best you can, while talking to him soothingly. After shaking down the thermometer and lubricating it well with petroleum jelly, lift his tail and gently push the thermometer in with a twisting motion. Insert the thermometer from one to three inches, depending on the size of your dog and hold it in place for at least two minutes.
After you remove the thermometer, wipe it clean and read the temperature by the height of the silver column of mercury on the thermometer scale. A temperature of 100.5° to 102°F degrees is normal.
Taking your dog's temperature by ear
When used properly, ear thermometers are a reliable and less invasive way to take your dog's temperature. An ear thermometer works by measuring infrared heat waves that are emitted from the dog's eardrum area. Be sure to place the thermometer deep into the horizontal ear canal to obtain an accurate reading. A dog's normal ear temperature is between 100° to 103°F. Note that ear thermometers are generally more expensive than rectal thermometers and, if not used properly, are less accurate.
When to contact your vet
Any time a dog's temperature falls below 99°F or rises above 103°F, you should contact your veterinarian. If your dog has a high temperature, it can be a sign that he is suffering from an infection or an illness. A low temperature, on the other hand, can indicate shock or other serious illness. In either case, it's best to err on the side of caution.
Taking Your Dog's Temperature at Home
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Jun 3, 2011 "Share your voice on Yahoo! websites. Start Here."
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When my dog got sick a couple of years ago one of the first things I did was take his temperature. Once I knew he was running a fever I called my veterinarian and we got in immediately. Giving the vet a heads up on what he may be dealing with can get your pet seen faster in emergency situations.
If a dog seems lethargic or overly tired or has little to no appetite for more 12 hours, it may have a fever. It's not difficult to take your dog's temperature at home. Doing so will help you assess if you have a medical emergency on your hands.
You can use a rectal thermometer, either digital or mercury, or you can use an ear canal thermometer. For rectal temping you'll also need a water based lubricant and rubbing alcohol.
Place the dog in a standing position. Ask for help from another adult if the dog is squirming or sitting down repeatedly. Shake a mercury thermometer to below 94F. Disinfect the thermometer with the rubbing alcohol and place a small amount of lubricant on the end. With your free hand, lift the dog's tail and insert the thermometer into the anus to about one inch or less. After insertion put your free hand under the dog's belly to keep them standing. Remove mercury thermometers after two minutes or digital when they beep.
When using an ear thermometer be sure to place it far enough into the ear canal. Do not attempt to use anything other than an ear thermometer specially made for pets. They have a longer arm for getting to the correct place in the ear canal. Follow the package instructions and remove when it beeps.
For best results, practice using this instrument before your dog has a fever. Take the dog's temperature both rectally and using the ear thermometer. Compare the two, they should be close to the same.
A dog's normal rectal temperature is anywhere between 100.5F and 102.5. The normal range taken from the ear canal is 100.0F to 103.0F. Contact your veterinarian immediately if your pet's temperature is less than 99F or over 104F. Take your dog's temperature sometime when he is feeling well so you have a comparison if the dog ever appears to be running a fever.
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