Sick Sense: How Dogs Smell Illness

It's not hard to see why our ancient ancestors recruited dogs to their domestic staff.

As well as being extremely intelligent, dogs are blessed with senses much more powerful than those of humans. In particular, their sense of smell is extraordinarily well-developed.

Dogs are capable of sniffing everything from drugs to electricity, underground gas pipelines to ovulating animals.

Recent studies suggest that dogs may even be capable of using their super-sensitive snouts to detect human illnesses from epileptic fits to cancers. Here are a few, remarkable facts about the canine's olfactory abilities:


Dogs can detect cancer in humans.
Scientists think that simply by sniffing samples of human’s breath, dogs can detect lung, breast and other cancers with an accuracy rate of between 88 and 97 percent. The accuracy rate of a multi-million-pound hospital scanner is between 85 and 90 per cent.
Dogs can also be trained to alert people with heart conditions they are about to suffer a seizure.

Dogs can also anticipate in advance when a person is going to have an epileptic fit.
A Canadian study found that dogs who lived with children prone to epileptic episodes behaved unusually in advance of the attacks.
Some dogs would lick the child’s face or act protectively. One dog even guided a young girl away from a set of stairs shortly before she had an attack. The dogs’ warnings came as early as five hours before the first symptoms of the epileptic episode were visible.
A separate study involving six dogs found that they could be trained to accurately warn owners who were about to suffer fits.
Health authorities around the world are now training “seizure alert” or “seizure response” dogs, some of which can predict fits, and all of which will respond in an appropriate way when an owner does have a fit. Some will be trained to stay with and guard the owner, and some even to press a button on a phone which dials the emergency services.

It remains a mystery how they are able to pick up on epilepsy in this way. Some think they pick up on tiny behavioural or scent cues. Others are convinced it is a reaction to electrical activity in the body. But the fact that dogs also respond to psychological seizures, which are non-epileptic and don’t display abnormal electrical activity, casts doubt on this.

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