Scorpion experts have found that scorpion species with smaller and more slender claws typically have more toxic venom.
But just as with bee stings, any scorpion’s sting can be fatal to a person who is severely allergic to it.
Toxicity of the venom also varies by species and prey. A species’ particular cocktail may contain many chemicals, some aimed at insects and some toxic only to mammals. The different chemicals cause many different kinds of damage and symptoms. Some merely produce pain and swelling and are believed to be protective.
Some, used for killing prey, cause severe neurological damage by blocking chemical channels in nerve cells. Some cause direct damage to the heart muscle. In humans, the toxic effects can lead to respiratory paralysis, extremely high body temperatures, dangerously low or high blood pressure, a rapid heartbeat, and other conditions.
The stings of most American scorpion species are not usually fatal; for example, the Arizona Poison and Drug Information Center says that only one of the thirty species in the state is regarded as life-threatening. But stings are much more perilous for children.