Arizona Bark Scorpion: The Only Dangerous Species in the U.S.

Of the 30+ scorpion species found in Arizona, only one — the Arizona bark scorpion (Centruroides sculpturatus) — produces venom potent enough to cause systemic, life-threatening symptoms. It is the most venomous scorpion in North America. Bark scorpions are common throughout Pinal County, Maricopa County, and the greater Phoenix metro area. Understanding the difference between a mild sting and a medical emergency can save a life.

Immediate Symptoms After a Bark Scorpion Sting

Symptoms begin within minutes of a sting and evolve over 1–4 hours. The initial presentation at the sting site includes:

• Intense burning pain — often described as worse than a bee sting, immediate and sharp
• Numbness and tingling radiating from the sting site
• Hypersensitivity to touch — even light contact causes severe pain (allodynia)
• Minimal visible swelling — unlike bee stings, bark scorpion stings rarely cause significant local swelling. Absence of swelling does NOT mean the sting is minor.

Systemic Symptoms: Grading the Severity

Bark scorpion envenomation is graded on a 4-level scale used by Arizona Poison Control:

Grade I — Local Effects Only

Pain and paresthesia (tingling/numbness) confined to the sting site. No systemic symptoms. Most adult stings fall in this category. Treatment: ice pack, OTC pain reliever, monitor for progression.

Grade II — Pain at Remote Sites

Pain and tingling spread beyond the sting site — up the arm or leg, or to the opposite extremity. Still no systemic symptoms. Monitor closely; call Poison Control at 1-800-222-1222.

Grade III — Systemic Neurotoxic Effects (ONE of the following)

• Cranial nerve dysfunction: blurred vision, abnormal eye movements (nystagmus), difficulty swallowing, slurred speech
• Skeletal neuromuscular dysfunction: muscle twitching, jerking, uncontrolled movement

Go to the ER immediately. Grade III stings require antivenom (Anascorp) and IV sedation.

Grade IV — Systemic Neurotoxic Effects (BOTH cranial and skeletal)

Simultaneous cranial nerve dysfunction AND skeletal neuromuscular dysfunction. This is a life-threatening emergency. Call 911. Children under 6 and elderly adults are at highest risk for Grade IV envenomation.

Symptoms Requiring Immediate ER Visit

Go to the emergency room immediately if you or someone stung experiences any of the following:

• Difficulty breathing or shortness of breath
• Uncontrolled muscle spasms or convulsions
• Abnormal eye movements or inability to focus vision
• Difficulty swallowing or excessive drooling
• Slurred speech or confusion
• Rapid heart rate or high blood pressure
• The victim is a child under 6 years old — children are far more susceptible to severe envenomation
• The victim is elderly or immunocompromised
• Symptoms are worsening after 30 minutes

First Aid for Scorpion Stings

1. Stay calm. Anxiety increases heart rate and speeds venom circulation.
2. Call Arizona Poison Control: 1-800-222-1222. Available 24/7. They will guide you through severity assessment and advise whether ER is needed.
3. Apply a cool compress (not ice directly on skin) to the sting site to reduce pain.
4. Take OTC pain reliever (ibuprofen or acetaminophen) for Grade I stings.
5. Do NOT: cut the sting site, apply a tourniquet, suck out venom, apply electric shock, or use home remedies. None of these work and some cause additional harm.
6. Remove jewelry near the sting site in case of swelling.
7. Monitor for 4 hours. Most symptoms peak at 2–4 hours post-sting.

Antivenom: Anascorp

Anascorp (Centruroides immune F(ab')2) is the FDA-approved antivenom for bark scorpion envenomation. It is derived from horse antibodies and administered intravenously in the ER. Clinical trials showed Anascorp resolves Grade III/IV symptoms within 4 hours in most patients. It is available at Banner Health, Dignity Health, and most major Arizona hospital systems. The antivenom is most effective when administered early — another reason not to delay ER care for severe symptoms.

Who Is Most at Risk?

Severe envenomation disproportionately affects:

• Children under 6: Their smaller body mass means a higher venom-to-body-weight ratio. A sting that causes mild symptoms in an adult can be life-threatening in a toddler.
• Adults over 65: Reduced physiological reserve makes systemic effects harder to compensate for.
• People with heart conditions: Bark scorpion venom causes catecholamine release, which can trigger arrhythmias.
• People with respiratory conditions: Venom-induced muscle dysfunction can compromise breathing.

Preventing Scorpion Stings at Home

The best treatment is prevention. Bark scorpions enter homes through gaps as small as 1/16 inch. Key prevention steps include:

• Seal all gaps around doors, windows, pipes, and utility penetrations
• Install door sweeps on all exterior doors
• Shake out shoes, clothing, and towels before use
• Use a UV blacklight flashlight to hunt scorpions at night — they fluoresce bright green
• Schedule quarterly perimeter treatments with a licensed pest control company
• Remove bark, wood piles, and debris from around the foundation