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Ask Dr. Knowledge

Questions on fire ants

August 2, 2010

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A fire ant bit (stung?) me last week, and it’s nasty. I don’t remember these things being around when I was a kid. Where are they from? Any suggestions for dulling the pain?

There are several types of fire ants. Those in Southern states are from South America; the ones up North are from Northern Europe. They can be found all the way up to the Arctic Circle.

As to how they got here, insects have plenty of ways to hitch rides in this era of global transport and commerce.

Fire ants can be hard to distinguish from regular ants. European ants are often reddish brown, but colors vary. They have been in Massachusetts since 1908 but seem to be on the rise lately.

South American fire ants tend to be quite red, but by now a good general rule is just not to play with ants.

Regular ants bite, and then spray formic acid onto the wound. This is a simple acid similar to the acetic acid of vinegar. The same acid is made in the plant world, accounting for part of the sting of stinging nettles. The acid causes irritation and pain, but not like what you get from fire ants.

Fire ants attack in a very different way. They bite to hold onto their prey with venomless jaws, and then sting, much as a wasp does. The venom in the sting is largely made of a toxic piperidine alkaloid called solenopsin. It also has proteins that trigger an allergic response, and the net effect is burning pain and inflammation.

If you’re stung, first make sure you’re not having a severe allergic reaction, which would be a medical emergency.

If it’s just pain, make sure the ants are off, wash with soap and water to remove what venom you can, and clean up with alcohol or another disinfectant for the bites.

Cold compresses can help, as can creams with cortisone or aloe vera, and oral antihistamines.

Ask Dr. Knowledge is written by Northeastern University physicist John Swain. E-mail questions to drknowledge@globe.com or write to Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819.