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For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
The horizontal fraction bar was introduced by the Arabs.
Certain chemicals, after ingestion, can be converted by the body into cyanide. Most of these chemicals have been removed from the market, but some old nail polish remover, solvents, and plastics manufacturing solutions can contain these substances.