Scorpion stings — although painful — are mostly harmless. About 30 of the estimated 1,500 species of scorpions can inflict potentially fatal stings. In the United States, only the bark scorpion, found mainly in the desert Southwest, has venom potent enough to cause severe symptoms. Elsewhere, lethal scorpion stings occur predominantly in Mexico, South America, and parts of Africa, the Middle East and India.
Scorpion stings are most serious in young children, older adults and pets. In the United States, healthy adults usually don't need treatment for scorpion stings, but if your child is stung, seek immediate medical care.
Source: http://www.mayoclinic.com