Most scorpion stings cause only localized signs and symptoms, such as pain and warmth at the site of the sting. Sometimes these symptoms may be quite intense, even if you don't see redness or swelling.

Signs and symptoms at the site of the sting may include:

• Pain, which can be intense
• Numbness and tingling in the area around the sting
• Slight swelling in the area around the sting

Signs and symptoms related to widespread (systemic) venom effects usually occur in children who are stung and may include:

• Difficulty breathing
• Muscle twitching or thrashing
• Unusual head, neck and eye movements
• Drooling
• Sweating
• Nausea and vomiting
• High blood pressure (hypertension)
• Accelerated heart rate (tachycardia) or irregular heart beat (arrhythmia)
• Restlessness or excitability or inconsolable crying (in children)

As with other stinging insects, such as bees and wasps, it is possible for people who have previously been stung by scorpions to also have allergic reactions with subsequent stings. These subsequent stings are sometimes severe enough to cause a life-threatening condition called anaphylaxis. Signs and symptoms in these cases are similar to those of anaphylaxis caused by bee stings and can include hives, trouble breathing, and nausea and vomiting.

Scorpions are arthropods — a relative of insects, spiders and crustaceans. The average scorpion is about 3 inches (7.6 centimeters) long. Scorpions have eight legs and a pair of lobster-like pinchers and a tail that curves up. They sting rather than bite, using the stinger in their tails. The venom itself contains a complex mix of toxins that affect the nervous system (neurotoxins).

Scorpions are nocturnal creatures that resist stinging unless provoked or attacked. They can control the amount of venom they release — depending on how threatened they feel — so some stings may be almost entirely venomless.

Certain factors can increase your risk of a scorpion sting:

• Geography. In the United States, scorpions mainly live in the desert Southwest, primarily Arizona, New Mexico and parts of California. Worldwide, they're found most often in Mexico, NorthAfrica, South America, the Middle East, and India.
• Environment. Bark scorpions live under rocks, logs and tree bark — hence, the name. You're especially likely to encounter one when you're hiking or camping. Bark scorpions are also the most common house scorpion, hiding in firewood, garbage pails, bed linen and shoes.
• Travel. Not only are you more likely to encounter more-dangerous scorpions while traveling in certain parts of the world, you might bring them home with you. Scorpions can hide in clothing, luggage and shipping containers.

The very old and the very young are most likely to die of untreated venomous scorpion bites. The cause is usually heart or respiratory failure occurring some hours after the sting. Very few deaths from scorpion stings have been reported in the United States.

Another possible complication of scorpion stings, though rare, is a severe allergic reaction (anaphylaxis).