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According to the American College of Allergy, Asthma & Immunology, more than 50 million Americans have some kind of food allergy. Food allergies affect between 4 and 6% of children, and 4% of adults, according to the CDC. The most common food allergies include shellfish, peanuts, walnuts, fish, eggs, milk, and soy.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.