The best thing for a scorpion sting:
- wash the area
- apply an ice-pack or cold compress
- consider aspirin or ibuprofen for pain and swelling
- wait it out
There is nothing else you can do. They can hurt. A lot. But generally aren't an issue.
The exception to this rule, is the Arizona bark scorpion which is found in the Sonoran desert through AZ and southern CA (the area you are headed to). These diminutive critters pack a powerful punch, and can lead to partial paralysis, seizures, and respiratory distress or failure. These symptoms are more common in the elderly, small children, or those with compromised immune systems.
Your best treatment is prevention:
- wait till you are headed to bed to roll out your sleeping bag
- shake out clothes and boots before putting them on
- Never, never, NEVER hike at night with a black light. This won't put you in harm's way, but seeing how many are actually out there will freak you out.
Just for grins (this is NOT a bark scorpion):
http://lbell.org/87/scorpius-maximus/