Any dog's sense of smell is among the keenest on land, but just like a person can lose much of his hearing or vision, a dog can lose much of her sense of smell as she gets older. Just how much she loses may depend on her age and health as well.
The largest dog brain is about one-tenth the size of a human brain, but the olfactory part of a dog's brain is a whopping 40 times larger than yours. Dogs also have up to 60 times as many scent receptors as humans. This means that dogs -- who interpret their world by smell the way you interpret yours by sight -- can have a sense of smell up to 10 million times more sensitive than yours.
A wet nose is irritating for people, but for your dog it's like putting on a pair of glasses. Wetness in a dog's nose captures odor particles and allows her to smell better. A dry nose, therefore, can diminish her ability to smell, which is why she may lick her nose whenever something grabs her interest. Also, dogs sniff in short bursts to hold scents that they will lose if they exhale. An overheated or fatigued dog who pants can, for the duration, lose up to 40 percent of her ability to smell.
Viral infections and allergies to dust or pollen can wreak profound havoc with a dog's ability to smell. Allergens may mask scents while nasal conditions, such as sinusitis or influenza, may considerably block her ability to smell. If left untreated, such conditions could permanently damage your dog's sense of smell the way prolonged exposure to loud noise can permanently damage hearing. If she is sneezing, pawing her face, excessively panting or producing mucus through her nose, get her to a veterinarian right away.
As with all mammals, dogs naturally lose some of their senses as they age. Their sense of smell is no exception, and while dogs almost never fully lose their sense of smell for reasons other than severe trauma or disease, their sense of smell does diminish in their senior years. A tell-tale sign that your dog is losing some of her olfactory abilities is an increased appetite for spicy foods that have strong, sharp odors.
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