What does “metallic taste” mean?

  Have you ever had the experience of having a “metallic taste” in your mouth? This is not a comfortable experience. At this time, there are often various problems in the body. Oral diseases, gastrointestinal diseases, mental diseases and even cancer may be the reasons for people’s mouth full of metallic taste. Why is this? How does the metallic taste come about?
Metal has no smell

  When using “metallic” to describe a smell, have you ever wondered, what kind of smell is it? We already know that if people want to smell an odor, odor molecules must come to the nasal cavity and be captured by the olfactory cells in the nasal cavity before the brain can perceive the odor. Gas molecules move by themselves, and liquids easily volatilize gaseous molecules, so they can easily produce odors that people can smell. But solids are different. Solid molecules are arranged in an orderly manner, and the intermolecular forces are stronger. It is difficult for them to jump out of the substance and into the nasal cavity. Therefore, solids usually have no odor. So, where did the metallic taste come from?
  It wasn’t until 2006 that people finally uncovered the nature of the metallic taste. Dietermar Greenman, a chemist at Virginia Tech in the United States, discovered the origin of the metallic taste using mass spectrometry. Greenman found that metals alone have no odor, but after contact with the human body, the so-called “metallic taste” appears. Greenman soaked coins containing iron alloys in sweat and blood successively. After smelling the “metallic smell”, he collected the odor molecules in a beaker, and then analyzed its composition with a mass spectrometer. The results showed that the blood-like metallic taste came from an organic substance called 1-octen-3-one, which is produced by the chemical reaction of ferrous ions in coins with substances in human body fluids.
  The reaction speed of ferrous ions and human body fluids is very fast, so as soon as the skin comes into contact with the metal, it can quickly produce an odor, which leads people to have the illusion that the odor is produced by the metal itself. Moreover, people are very sensitive to the smell of 1-octen-3-one, which can be smelled at a concentration of only 50 nanograms per cubic meter, so the so-called “metallic smell” appears. Because the blood of many organisms, including humans, contains ferrous ions, the blood also smells like a “metallic smell”, and the reason why humans are so sensitive to this smell is probably due to the ability given by evolution. After all, blood is for survival. necessary substances.
  In addition to the bloody smell, the metal sometimes produces a garlic-like odor, which is the smell of some organophosphorus compounds. Iron and steel products are not actually pure metallic iron, they have carbon and phosphorus in them. After iron and steel products are attacked by acid, some small organophosphorus molecules, such as methyl phosphine and dimethyl phosphine, are released. Both molecules are easily smelt, and when phosphorus levels reach 3 to 6 nanograms per cubic meter, people will smell a metallic smell similar to the smell of garlic.

Where does the metallic taste come from?

  So why do people sometimes feel a metallic taste in their mouths?
  Since blood also has a metallic taste, some diseases that cause congestion in the mouth and nose can cause people to smell metallic. Gastroesophageal reflux disease is a chronic digestive tract disease. After eating, stomach acid will flow back into the digestive tract, causing burning and discomfort. Sometimes stomach acid will reach the mouth and destroy the oral mucosa. When blood flows out, people will smell it. Metallic taste. Oral diseases such as gingivitis and periodontitis are also possible causes of a metallic taste in the mouth.
  Certain toxic substances can also make people feel full of metallic taste, such as lead, cadmium, chromium and other heavy metals and arsenic, benzene, carbon disulfide and other substances, these substances will enter our body and contact with our respiratory tract and skin, like ferrous ions Reacts with the body’s organic matter to produce a metallic taste in the mouth.
  In addition to actually having substances that give off a metallic taste, dysgeusia can also make your mouth feel metallic. Head trauma directly damages the nerves that control our sense of taste and smell, and any changes to these nerves can permanently alter our perception. Neurological disorders such as multiple sclerosis and facial nerve palsy can also disrupt the central nervous system, which can affect the body’s sense of taste. Cancer treatments — Radiation and chemotherapy may destroy taste and smell receptor cells, thereby altering the sense of taste. More than half of those with altered tastes thought they smelled metallic.
  There are also drugs that can cause dysgeusia, such as antibiotics, lithium (used to treat mental illness), certain heart medications, and multivitamins. They disrupt the sense of taste in different ways, with some drugs disrupting taste by causing dry mouth and reducing saliva production, and others by disrupting the signals that taste buds send to the brain, creating the illusion of metallic taste. These types of taste disorders usually return to normal after a period of discontinuation of the drug.
  Now you know, it’s not a good thing to have a metallic taste in the mouth, but from another perspective, this smell can give people a hint, which is helpful for people to deal with the hidden dangers caused by diseases or poisons as soon as possible and avoid causing more harm. .