Is the Arizona Bark Scorpion Deadly? Venom and Real Risk

How dangerous is a bark scorpion sting?

For most healthy adults, a sting from an Arizona bark scorpion is an intensely painful but short-lived event. The typical symptoms are sharp, burning pain at the sting site, followed by numbness and tingling that can spread along the arm or leg. Many people describe a sensation like small electric shocks. There is usually little swelling or redness, which surprises people who expect a visible wound.

These local symptoms normally fade within one to three days. In a small share of cases, especially in young children, the venom affects the nervous system more widely. Signs of this can include restlessness, uncontrolled or roving eye movements, drooling, slurred speech, muscle twitching and jerking, and trouble swallowing or breathing. These severe reactions need hospital treatment and are the reason Arizona’s poison centers take every sting in a small child seriously.

Why is bark scorpion venom so painful?

Scorpion venom is a mixture of small proteins, most of them neurotoxins. In the bark scorpion, the key toxins act on sodium channels, the tiny gates in nerve cell membranes that control electrical signals. By keeping these channels open or making them fire too easily, the venom makes nerves send a flood of signals. The result is pain, tingling and, in severe cases, involuntary muscle movements.

The venom evolved to subdue insects and spiders, not people. A scorpion often injects only a small amount, and some defensive stings may contain little or no venom at all. That variation helps explain why two stings from the same species can feel very different.

How many people are stung, and how many die?

Bark scorpions are common in and around homes across southern and central Arizona, so stings are a routine part of desert life. Arizona’s poison centers receive thousands of calls about scorpion stings every year, and most of them involve bark scorpions.

Deaths, however, are now very rare. Several child deaths were blamed on scorpion stings in Arizona in the first half of the 20th century, before modern intensive care. Since the late 1960s, only a very small number of deaths have been attributed to the species. Better emergency care has made the biggest difference, along with antivenom: Arizona hospitals used a locally made antivenom for decades, and in 2011 the US Food and Drug Administration approved an antivenom for Centruroides scorpions.

Who is most at risk?

Young children face the greatest risk. A bark scorpion delivers roughly the same amount of venom whether it stings a toddler or an adult, but a child’s body is much smaller, so the dose relative to body weight is far higher. Children also cannot always explain what happened, so a sting may be noticed only when symptoms begin.

Older adults and people with heart or breathing problems may also react more strongly. As with bee stings, a few people develop an allergic reaction to the venom, which is a separate and potentially serious emergency.

How does it compare with dangerous scorpions elsewhere?

Worldwide, scientists estimate that there are more than a million scorpion stings each year, causing a few thousand deaths, mostly in parts of North Africa, the Middle East, South Asia and Latin America. Of more than 2,500 scorpion species, only about 25 have venom considered capable of killing a healthy adult.

The North African deathstalker is generally considered far more dangerous than the bark scorpion. Mexico, which has many dangerous Centruroides species, records some of the highest numbers of stings in the world. For a wider view, see the most venomous animals in the world.

Why do people get stung?

Bark scorpions are not aggressive. They sting in self-defense when pressed against skin. Their habits explain most stings:

• They climb walls and ceilings and like to rest upside down under objects, so a hand that reaches under a board, pot or ledge may touch one.
• They hide by day in shoes, gloves, folded clothes, bedding and towels left on the floor.
• They are active at night, when people walk barefoot across patios, yards or floors.
• They enter homes through very small gaps, around 1.6 mm (1/16 in) wide.

Simple habits lower the risk: shake out shoes, gloves and clothes before putting them on, wear shoes outdoors at night, keep beds away from walls in scorpion-prone homes, and never pick up a scorpion. A UV flashlight makes bark scorpions glow at night, so they are easier to see and avoid; learn why in why scorpions glow under UV light.

If someone is stung and develops severe symptoms such as trouble breathing, unusual eye movements or uncontrolled twitching, or if a young child is stung, seek emergency medical help immediately or call 911.

Myths about bark scorpion stings

“Small scorpions are more dangerous than big ones.” There is a grain of truth here: many dangerous scorpions, including the bark scorpion, have slim pincers and a thin tail, while large, thick-clawed scorpions often have weaker venom. But size alone is not a reliable rule, and no scorpion should be handled.

“A bark scorpion sting is always fatal without treatment.” This is false. Most stings in adults resolve on their own, although they can be extremely painful. Medical advice is still important, especially for children.

“Scorpions hunt people in their beds.” Scorpions do not seek out people. They wander at night looking for insects, and a sting happens only when one is accidentally touched or trapped.