Bitter raw almonds are poisonous, according to the Huffington Post. They contain a substance that breaks down into cyanide. Cooking bitter almonds destroys the poison.
The Huffington Post explains that there are two types of almonds: bitter and sweet. Sweet almonds are cultivated, marketed and consumed in the United States and are not poisonous.
The L.A. Times notes that consuming bitter almonds can be fatal depending on the size and quantity of the nuts eaten, the concentration of the toxin in the nuts and the sensitivity of the person. It is estimated that consumption of 10 to 70 bitter almonds is potentially fatal to a 150-pound adult whereas ingestion of just a few nuts might be enough to be lethal to a child.