Apricot kernels are the little seeds found at the center of an apricot. Although similar to almonds, which are Paleo-friendly, apricot kernels contain very high levels of cyanide. On average, each apricot kernel contains 0.5 mg of cyanide. A fatal dose of cyanide for humans is usually around 1.5 mg/kg of bodyweight. This means that consuming just a few ounces of apricot kernels can lead to symptoms of cyanide poisoning, including nausea, fever, rash, headaches, insomnia, increased thirst, weakness, lethargy, nervousness, aches and pains in joints and muscles, and a drop in blood pressure.
Although they are seeds, and as such, may appear to be a good Paleo-friendly option, we generally advise against eating things that are poisonous. Mark Sisson included a break down of the benefits and dangers of eating apricot kernels on his blog.