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Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
The horizontal fraction bar was introduced by the Arabs.
Historic treatments for rheumatoid arthritis have included gold salts, acupuncture, a diet consisting of apples or rhubarb, nutmeg, nettles, bee venom, bracelets made of copper, prayer, rest, tooth extractions, fasting, honey, vitamins, insulin, snow collected on Christmas, magnets, and electric convulsion therapy.
More than 50% of American adults have oral herpes, which is commonly known as "cold sores" or "fever blisters." The herpes virus can be active on the skin surface without showing any signs or causing any symptoms.
In 2012, nearly 24 milliion Americans, aged 12 and older, had abused an illicit drug, according to the National Institute on Drug Abuse (NIDA).