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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.
Fungal nail infections account for up to 30% of all skin infections. They affect 5% of the general population—mostly people over the age of 70.
A strange skin disease referred to as Morgellons has occurred in the southern United States and in California. Symptoms include slowly healing sores, joint pain, persistent fatigue, and a sensation of things crawling through the skin. Another symptom is strange-looking, threadlike extrusions coming out of the skin.
Hyperthyroidism leads to an increased rate of metabolism and affects about 1% of women but only 0.1% of men. For most people, this increased metabolic rate causes the thyroid gland to become enlarged (known as a goiter).
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.