11Dandruff
Dandruff is caused by a fungus that uses lipase to digest lipids, so it lives in areas with many sebaceous glands. The lipases break down skin, as well, and when the fungi grow too fast, larger flakes of skin (dandruff) come off as the epidermis is replaced from the levels below.
12Sickle-cell anemia
Sickle-cell anemia protects the carrier from malaria, which is why it is seen mostly in people of African descent.
13Kidney stones
Kidney stones can grow until they fill up all the crevices in your kidneys and resemble deer antlers; they're called staghorn stones
14Dyslexia
Dyslexia isn't characterized by the reversal of letters or words and mirror writing. It's a disorder of people with at least average intelligence who have difficulty spelling words, reading quickly, writing words, sounding words out, pronouncing words read aloud, understanding what they read.
15Heartburn
Heartburn actually has nothing to do with the heart at all. It occurs when the sphincter muscle at the end of the esophagus abnormally relaxes and fluids from the stomach, such as stomach acid and bile, flow back up into the esophagus. It is more likely to happen when bent over or lying down.
16Crohn's disease
Complications of Crohn's disease include fistulas between your gut and several abdominal organs, resulting in passing gas and feces into places like your skin, urine, or vagina.
17Flu
The flu presents as asymptomatic 75% of the time in otherwise the young and healthy, and yet is still highly contagious and deadly to vulnerable populations.
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18Acid reflux disease
Sufferers of acid reflux disease occasionally report a distinct feeling of something stuck in their throat, often lasting for days. This happens because the acid causes the throat tissues to swell, creating a lump feeling.
19Canker Sores
Canker Sores are a mystery to modern medicine, they don't know why they happen and there is no cure.
20Yellow fever
Yellow fever came to the Americas aboard slave ships. Two hundred years later, it helped end slavery in Haiti. An epidemic broke out during the Haitian Revolution, killing two-thirds of the French army. It killed almost none of the slaves. France was therefore forced to surrender the island.