You may as well give in and let that wash-clothed-sized pink tongue give your face an affectionate lick. Otherwise the look of rejection in those deep sad eyes might just break your heart.
The chances are that you are already an ardent dog lover anyway, if you find yourself the object of a canine licking on a Swiss mountain pass, 2,500 metres above sea level -unless you were just dug out of an avalanche.
The dog-rescue heydays are past, but now one of the St Bernards that still live around here, perhaps Kosima, Wenda or Bounty, will lead you along trails trodden by their ancestors for centuries in search of stranded travellers or avalanche victims.
Now they do it for pleasure.
"Physical closeness, even to strangers, just comes naturally to our 30 St Bernards," says Clementine Coquoz, a dog carer at the Barry Foundation, who is rather dwarfed as she stands between these legendary 80-kilogram canines.
Twice a day during the summer, when the snow has gone and the mountains are green, the dogs go walking with visitors for 90 minutes.
"The animals need lots of exercise and contact anyway," says Doris Kuendig, spokesperson at the Barry Foundation, which took charge of the dogs in 2005 when new Swiss animal legislation meant the nearby Augustinian monastery, their traditional home, couldn't keep them.
In another break with tradition, the dogs don't go up onto the pass while it is still snowed up. Anyone wishing to walk with St. Bernards earlier in the year can do so in the vineyards along the Valais wine route near Martigny.
This is the dogs' winter quarters and also the site of the St Bernard museum.
But the best option for animal lovers is a summer tour with the giant dogs high up on the border pass between the Rhone Valley on the Swiss side and the Aosta Valley on the Italian side. This is the real homeland of the St. Bernard, and also the erroneous origin of their famous - and fabled - prop, the brandy keg with a Swiss cross emblem.
Today, Bounty has one hanging from her neck, but a little reluctantly.
"She senses she is doing the tourists a favour by being photographed with it," says Clementine. Once the photo session in front of the picturesque mountain scenery is over, this awkward piece of paraphernalia is removed.
It's rather a disservice to the breed's distinguished record as rescuers that people erroneously talk about how frozen victims were revived with tots of rum. It was the dogs that did the saving.
But that red herring aside, the stories are largely true about dramatic canine mountain rescues over the centuries, and especially regarding the original "keg-wearing" dog called Barry, which sniffed out buried soldiers during Napoleon's retreat through the pass in the early 19th century.
None of the dogs used by the Augustinian monks was as skilled as Barry, a dog credited with rescuing at least 40 people from an icy death before he died in 1814. Altogether, some 2,000 lives were saved with the help of St. Bernards from the time when the monks began their daily searches of the highlands from the mid-17th century.
The monks were often given robust sheepdogs by local farmers, who regarded Bernard of Menthon, the archdeacon of Aosta, who in 1050 founded the monastic mountain refuge for travellers, as a saint.
Over time a keen rescue instinct was bred into the emerging breed, which was first mentioned by name in 1709. The dogs were originally raised to act as guard dogs for the hostel, or hospice as the monks call it, before they became mountain rescue dogs.
Still open to all, the hospice is located at the Gran San Bernardo, the highest point of the 2,000-kilometre Via Francigena, a pilgrimage route that runs from Canterbury in southern England to Rome.
The monks' choirmaster Raphael Duchoud says giving up the dogs was "the best solution".
"At that time Switzerland tightened its animal protection law, and we would have had to hire certified professionals and veterinarians (if we had kept them)," he explains.
This year, the Barry Foundation is marking its 10th anniversary with a series of events, including a strong turnout by the legendary dogs, and perhaps even a toast or two of brandy from a little wooden keg.