Do you remember the Whole Foods almond recall in late 2014? The recalled almonds were different from the ones we normally eat. The almonds we usually see in stores are known as sweet almonds, but their close cousin – the bitter almond – contains dangerous levels of hydrogen cyanide. Bitter almonds aren't very common in the U.S., but in Europe many chefs love them [source: Karp].
Children who ingest just a few raw bitter almonds are at risk of death. Adults can eat far more and survive, though you would experience some symptoms that might make you wish you hadn't. Hydrogen cyanide poisoning includes symptoms from dizziness and headache to vomiting and convulsions, depending on how much you've eaten [source: Food Safety News].
As with all of the foods on this list, proper cooking is the key to making bitter almonds safe to ingest. Blanching or roasting destroys the hydrogen cyanide in bitter almonds, but there doesn't seem to be any solid research on what temperatures you need to reach or for how long [source: PICSE]. If you're planning to cook with bitter almonds, your best bet is to follow a tried-and-true recipe.