We should not be allarmed by an occasional scratching, but scratching and licking persistently, could indicate illness..
  There could be different causes: an irritation of the skin (due to parasites, erythema, and such like), a small injury we failed to spot (and which could be infected if repeatedly licked) or even a problem of pychological nature (sometimes dogs lick themselves to unload a heavy stress).
  If the dog scratches persistently his ears, shakes his head or keeps the headleaning to the side he probably suffers from ear-ache. The cause could be either an otitis or the infiltration of an alien organism.

  If the dog vomits food, he could have eaten too fast.
  If he vomits foam, he might have eaten grass or irritating or toxic substances, he could also have worms or a gastric irritation.
  If he vomits blood he might have swallowed stones or bones, or suffer from stomach or intestinal deseases.

  If the dog vomits blood go to the veterinarian's at once.
  If he vomits food or foam and he behaves apathetically, go to the veterinarian's.
  If he vomits food or foam but shows no other worrying symptoms, and looks fit and playful:
  a) if he vomited just once or twice, don't do anything;
  b) if he vomited three to four times, keep him fasting for a day and see what happens;
  c) if he keeps vomiting five or more times, go to the veterinarian's.

  The dog might have had too much water to drink, be overfed, suffered an abrupt change of diet, be infested by worms, or picked up an infectious diseases.

  If the dog is a puppy: ignore if it's a one-episode symptom; if it happens again, go to the vet's and have the faeces examined.

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  If the dog is an adult: ignore if it's a one-episode symptom; if it repeats once, keep him fasting for a day; if it happens again, go to the vet's and have the faeces examined.

  Be careful: see always the doctor if there is presence of worms or blood in the faeces.

  Dehydration, he might have swallowed bones, stones, and so on.

  Unless the dog shows other symptoms (such as vomit, apathy, ache at abdominal palpation), keep him on half of his usual food ration for two days and do no more.
  Later on, if the problem persists, keep the dog fasting and two-three times a day give him a spoon of vaseline oil). If the intestine does not respond, give him an enema; if still not responsive, call the vet.

  This is one of the most serious problems common to all giant breeds of dogs; it is a lethal pathology if not detected and surgically solved in time.
  Although it is an very much studied pathology, it is still hardly comprehended and there is no certain "recipes" to prevent it: the only sure thing to do is to run tests on the air contained in the stomach of dogs who suffer from stomach torsion; this air is usually atmospheric and not produced by digestive fermentation.
  Another common cause of this illness is the ingestion of large quantities of water.
  Even if the amount of food the dog ate doesn't seem very relevant considering the aforementioned facts, all breeders believe proper feeding could be a good preventative measure; different breeders have, however, different opinions of which all certainly make sense.
  Some feel that is better to divide a food ration in two halves, to avoid stomach overload; others prefer a single meal to restrain the time of digestion (virtually the dog doesn't go on "digesting all day", and the period of risk becomes just one instead of two).
  But all of them agree on the fact the dog should not perform any physical activities while digesting. It would be best for him to lie down and rest (something a Saint Bernard loves to do spontaneously after a meal, feeling perhaps it is the best thing for his health).
  Today we assume that at the root of stomach torsion is a genetical predisposition, as some blood-lines are affected more then others: the most relevant characteristic is the chest depth.
  But we know for a fact that dogs at greater risk are the ones who ingest more air when they eat. When does a dog ingest air? When he stuff himself: this might occur if the dog is nervous or in competition with other subjects or simply because he likes his meal... a little too much!   The first thing to do is to avoid some of the probable causes: do not feed more than one dog at a time and choose food that is less attractive to the dog .   
 Another thing you should absolutely avoid is to have your dog drink "like a camel": you could do it by rationing his water, or avoid that his thirst becomes excessive (do not keep him in a too warm environment, don't make him run in the sun and so on).

  Giant dog breeds are the ones at most risk from dysplasia: it is however well known it is not an exclusively genetic illness, but the outcome of a combination involving a genetic and an environmental component (according to some authors the latter is the decisive one). Today surgery is able to help dogs afflicted by this illness improving their quality of life, but the most important fact remains a good prevention.
  Only the breeder is in charge of the genetic prospective, he must assure not to use in breeding subjects affected by displasia, especially if those subjects come from "families" which carry the illness.
  The owner has his share of responsibility too: he must provide a proper environment for his dog, care for his feeding and exercise.
  In the chapter on feeding we already mentioned the major risk factors: overload of calcium and a general energy overload for the growing dog.
  Proper physical exercise is of as much importance: for puppies up to six months it should be cut down to minimum: only strolls and light trot.
  From six months to a year of age a little exercise won't harm (although jumping is strictly forbidden), and after the first year you can switch to intensive exercise.
Among the medical exams the most important are the x-rays, which allow you to always have a clear picture of the dog's health situation and to act (if needed) promptly. To follow is an ideal prospect of check-up each owner should make undergo his Saint Bernard:
  - at five months: exam of the distal cartilage of the radius and ulna;
  - at five month and a half: x-ray of the elbow (in the Saint Bernard the dysplasia of the elbow is usually caused by failure of the bond of the anconeal junction, and it can be surgically successfully mended at this age by removing the bone fragment that failed to bond; later the problem is much more difficult to solve);
  - at eighteen months: x-rays of the hips.
  Needless to say the subjects carriers of dysplasia should be excluded always from breeding: the health of a breed is not in the hands of the "official" breeders only, but in those of private breeders as well, who should feel their share of responsibility and avoid to breed puppies who could be ill or unhappy.

  The particular conformation of a Saint Bernard's eye puts him at risk of pathologies concerning eye-lids: such as entropion and ectropion (respectively an eye-lid turned in and out), which require correctional surgery.
  It is important to tell apart a true pathology from a... rhomboid-shaped eye, which is the proper shape prescribed by the Standard! Unfortunately this is not a joke, because some veterinarians, unfamiliar with the breed, corrected surgically perfectly healthy eyes.

  The most frequent cardiac disease are basically two: dilative myocardiopathy and pericardial effusion (the latter one is more common in the Terranova).
  The frequency of these deseases seems to be connected to blood-line transmission (pericardial effusion also seems to be an autoimmune phenomenon), therefore all a private owner could do is to collect as much information on the family anamnesis of the puppy he's interested in.
  An early diagnosis (by a simple cardiologic exam, better if joined with a chest x-ray) will allow the dog to live longer and have a better quality of life, with proper pharmacologic care.