If you suffer from chronic halitosis - bad breath - you will probably be the last person to know it. Even Prof. Mel Rosenberg of Tel Aviv University's human microbiology and immunology department, and one of the world's leading experts on the subject, can't tell for sure whether his own breath is pleasant; he needs a "confidant" to check it. Most people, even those you are close to, are very reluctant to tell others they have halitosis, he explains. Doctors or dentists asked to smell their patients' breath are often reluctant to tell them the truth because they fear losing them as clients, he notes. But even if they do tell you, few - except for experts like Rosenberg - can figure out what causes a specific case. Halitosis, suffered by an estimated one-fifth of the population, is an embarrassing - and funny - subject. However, individuals who even mistakenly think their breath stinks have been known to commit suicide, try compulsively to hide it or isolate themselves from social contact for decades. Studies have found that people with halitosis are less likely to be promoted at work, and most people wouldn't date somebody who has bad breath. Some mouthwash and toothpaste advertisements use the "fear factor" by presenting single women who "would have gotten married" if their breath had been fine. HALITOSIS IS no laughing manner. Indeed, some of the clients at his private clinic insist he has changed their lives. Now Rosenberg, who has smelled the breath of thousands of people and survived, explains everything in his new, well-titled $27 volume, Save Your Breath: Turning Bad Breath into Best Breath. The 168-page, $27 softcover just issued by SmellWell Publishing offers relief to people who have foul breath, those who don't but fear they do, and relatives and friends who want to help them - as well as dentists, dental hygienists, general practitioners and ear-nose-and-throat (ENT) specialists. It took him two decades to research and write it - ever since the Ottowa-born microbiologist visited the TAU lab of Prof. Eugene Rosenberg (no relation) who with colleagues were researching solutions to dislodge oral microorganisms. Although Mel, who came on aliya at the age of 17, had wanted to sell pianos, his wife Shulamit persuaded him to return to university for a doctorate. He worked with Eugene on bacteria that can digest petroleum and thus reduce pollution. When he noted that the bacteria stuck to the oil globules and was asked to find out why, he decided to apply the principle to the question about whether bacteria that cause halitosis also stuck to oil droplets. Mel and colleagues found that microorganisms that form plaque on the teeth have a "dramatic propensity for sticking to oil droplets." That discovery eventually led to his development of the scientifically based alcohol-free Assuta mouthwash (known as Dentyl pH in the UK where it is known as Dentyl pH, now one of two leading brands in that country and sold around the world. It works in two phases, changing from one color to another, and must be shaken before use. BUT THE BOOK is not a mouthwash commercial, but rather an in-depth but explanation of what causes halitosis and what can be done to eliminate it. Rosenberg - who says his favorite scent is that of a rose, followed by babies and "Canadian autumn smell," and who has a "curious nose" - writes that bad breath cannot be self-diagnosed. There are many commonly used techniques, such as cupping your hands over the nose and mouth and breathing out; licking your wrist, letting the saliva dry and then smelling the residue; smelling a phone receiver after you speak into it; smelling the food you just took a bite of; smelling the toothbrush, floss or toothpick you just used; or hiding under your blanket and smelling your own breath. Rosenberg insists none of these methods is accurate because one is inured to one's own smell; one's breath emerges horizontally while one inhales vertically; and because the main source of bad breath - bacteria flourishing on the back of the tongue - is not reached. Everyone worries sometime about having bad breath, says the microbiologist, especially if they encounter a relative who has it. "When we smell how bad their breath is, we become even more worried about our own." His own uncle had it, he recalls. Some people mistakenly believe they inherited the condition. So where does chronic bad breath come from? According to Rosenberg, in 85 percent to 90% of cases, it originates in the mouth (mostly the back of the tongue), with the rest from the nose (due to post-nasal drip or sinus infections). Bad breath originates in the stomach or lungs very rarely. The smell, which varies according to the source, is usually caused by bacteria breaking down proteins (including food stuck between the teeth such as meat, fish and milk), mucous and plaque on the teeth, as well as rotting gums. While Rosenberg smells the breath of people coming to his clinic, he writes that people worried about the problem can more cheaply ask a trusted close friend or relative to do so. Such a person may already be aware that you have halitosis, so "you have little to risk." He or she can probably determine whether the odor comes from the mouth or nose. Sometimes, such confidants go with the patient to the dentist or breath clinic. While a good dental cleaning or consultation with a physician can eliminate the cause of the odor, a confidant can serve as a "monitor" to ensure that it stays away. Yet some cases are more complicated than that. If the same odor comes from both mouth and nose (which is rare), Rosenberg says it may be related to tobacco smoke, onions, garlic or alcohol. A dentist should be consulted if the smell comes from the mouth, an ENT specialist if it's from the nose, and a physician is it's emanating from both organs. There are billions of bacteria in the mouth, and those that survive in very cramped conditions are responsible for the volatile molecules that cause the odor. Some of the resulting gases contain sulfur, nitrogen or other elements, each of which produce a characteristic smell. Antibiotics are often very successful at killing the offending (offensive) bacteria, but they cannot be taken permanently, and a week's dose loses its effectiveness a few weeks later, says Rosenberg, who not only conducts research at TAU but also teaches dental and microbiology students and ENT residents. Bacteria need a suitable environment to flourish. In the "tropical rain forest" that is the mouth, saliva is the moisture; 35 degrees Celsius and a neutral pH (neither acidic nor alkaline) make their home hospitable. Saliva helps you chew food, swallow and talk, but it also provides the necessary moisture for the growth of bacteria. Fortunately, saliva also helps wash billions of bacteria out of the mouth, to be destroyed in the stomach. There is thus a constant battle in the oral cavity, but the individual has to help the "good side" by maintaining clean teeth and removing the bacteria on the back of the tongue as often as possible. People suffering from xerostomia (lack of saliva) due to radiation therapy, autoimmune disease or taking a variety of medications rarely suffer from bad breath, but they are at higher risk of developing dental decay. When one's saliva flow is meager, as during a night's sleep, the person often wakes up with bad breath due to the lack of flow. Eating a good breakfast comprised of natural fiber (such as vegetables, fruits and whole grains) will get the saliva going and naturally dislodge bacteria from the surfaces inside the mouth, continues Rosenberg. It was not he but a dentist named G.L. Grapp who in 1933 published a paper that concluded most bad breath comes from the back of the tongue towards he tonsils. He even designed a tongue cleaner and showed that breath improve when the bacterial layer on the piece of muscle is removed. The British Dental Association office in West London has an antique collection of European tongue cleaners. Ancient Indian medicine also used tongue cleaners thousands of years ago. Today, says the author, Western medicine "largely ignores the tongue," which rarely get infected even after it has been bitten by its owner, but whose "shag-carpet-like topography accumulates bacteria in its crevices." Rosenberg says that tonsils and adenoids are almost never responsible for bad breath, even if infected. He would not recommend surgery to remove them unless they are verified as the cause of halitosis; all other oral cavities are completely ruled out at the source; simpler treatments don't work; the odor problem is chronic and significant; and there are no other good medical reasons for operating. Any surgeon who urges it despite these conditions would be irresponsible, states Rosenberg. Little whitish-yellowish stones called tonsilloliths (tonsil stones) - found in about five percent of a studied population - scare people when they are coughed out. But even though they produce a foul smell when pressed between the fingers to release the gas from calcified organic material, they do not necessarily cause bad breath. This, says the author, does not deter some from the risky practice of poking them out of their tonsils with a pencil. Smoking, of course, causes the mouth (and whole body) to stink. Rosenberg knows that the dangerous habit also "exacerbates the accumulation of viscous, awful-smelling post-nasal drip on the tongue - a wicked combination indeed." Newborn babies have a lovely smell, he writes, as their mouths are sterile in the womb. They shouldn't suffer from bad breath as toddlers, unless their teeth are covered with plaque or they suffer from streptococcal infections in the throat or post-nasal drip on the tongue. A horrible smell emanating from a child, Rosenberg has found from experience with clients, can sometimes be attributed to pieces of paper, pea and corn kernels, seeds, small batteries, insects ad even snails being poked up into their nostrils. If the foreign material absorbs moisture, it quickly cultures a horde of bacteria and smells awful. He says that some hospital doctors perform an X-ray (which doesn't always show up such objects) instead of just looking up their noses. Saliva flow often ebbs in the elderly; they often take many medications; can't afford proper dental care; prefer to eat soft foods; and sometimes can't chew properly. This can lead to dental decay, periodontic disease and bad breath. Rosenberg recalls a charming old lady whose grandchildren refused to kiss her because of her breath. Her dentist consulted him, and together they cleaned her dentures ultrasonically, solving the problem. That case, the author recalls, "helped prompt me to open my first private breath consultation practice in 1988." Women seem more sensitive to odors than men, probably due to hormones involved in their menstrual cycle, and they also judge their own breath more harshly. Rosenberg tells tales about a pregnant woman whose intensified senses made her complain about her husband's breath, and a husband who falsely accused his wife of having bad breath after she demanded that her spouse "fulfill his marital duties" more frequently. These problems did not have to be solved by a dentist. Egyptian papyrus segments from over 3,500 years ago suggest concoctions to fight bad breath, so mankind has been aware of it for a long time. The Talmud even notes that working with flax can cause bad breath; a Bar-Ilan University textile history expert has explained that licking flax fibers to spin them damages lips and causes bad breath. Having a spouse with chronic halitosis is even sufficient for getting a divorce, according to ancient Jewish law and other religions (the Prophet Muhammed once asked someone to leave the mosque because of bad breath), but fortunately, it can be treated today. A six-page letter of thanks sent to Rosenberg by a former client he calls "Daisy" and published in full is a moving document that he uses to show how halitosis can cause a life-long crisis. After a boyfriend casually said her breath was bad (but it wasn't), she developed an obsession about it, underwent extreme medical tests, avoided social contact, refused to be in a vehicle without the windows open, and married the wrong man mostly because he complimented her on her breath. After being told by the expert that she definitely didn't have halitosis, she gradually dropped her strange behaviors and became convinced, enabling her to divorce, marry a compatible man and part with her obsession. Daisy got her life back. Prof. Mel Rosenberg and information about his book can be accessed at www.smellwell.com, www.melrosenberg.com, firstname.lastname@example.org or 052-2946820.