Without realizing it, you kneeled or set down your blanket on top of a fire ant mound, and now you’re paying a painful price for your intrusion. “They’re really a miserable ant species,” says Michael Merchant, PhD, a professor of entomology at Texas A&M University in Dallas. Dr. Merchant says that when he and his wife moved to Texas many years ago, they had a horrific, picnic-spoiling fire ant experience like the one described above. And as the species has spread across much of the southern half of the continental United States, many people have had similar run-ins with fire ants. (1) “In Texas and a lot of the Southwest, they’ve made going outside and sitting on the ground a pleasure of the past,” he says. It’s thought that fire ants arrived in the United States in the 1930s via cargo ships traveling from South America. (2) And since then, they’ve become an “ecological disaster,” Merchant says. “Wherever they go, they lower biodiversity and attack other ants and animals.” Unfortunately their prey includes humans. Fire ants are among the very few types of domestic ants that frequently bite people. But saying that these ants “bite” is actually inaccurate. “Fire ants don’t bite, they deliver a sting via their tail,” Merchant says. “Only the females sting, and their stinger is very sharp and delivers venom.” Fire ants aren’t a problem in most places that experience freezing temps during winter. But there are other species of ant that live in northern states that do occasionally bite or sting. In some cases, those attacks can be quite serious.

How You Know It’s a Fire Ant Bite or Sting

“It starts out as a small, red spot, and, after a day or two, a white pustule forms that’s itchy and a little bit painful,” Merchant says. It’s possible to experience just a single sting from a lone fire ant. “You may be outside working in a garden or something and get just one on your arm or leg, but commonly people make the mistake of stopping and standing on a mound without realizing it, so they end up covered and they get hundreds of stings.” A fire ant’s stinger is not barbed, so it can sting a person multiple times. “You may see a row of red marks, and that’s where one ant has grabbed on and stabbed its stinger down in a semicircle,” he says. Of course, if you’ve picked up multiple fire ants, you’ll know what’s stinging you because you’ll see and feel them on your skin. But if you’re stung just once and don’t see the fire ant, you’ll know it by the fiery sensation and the white pus-filled blister that forms a day or two later.

What to Do About Them and When to Seek Medical Attention

Merchant says that, in most cases, fire ant stings don’t require any medical treatment. They’ll itch for a few days, but they’ll go away within a week to 10 days. “But some people — about one in 100 — will have a more serious reaction,” he says. (And in rare cases it can be lethal if the allergic reaction is not treated immediately.) (3) Head to the ER if you notice any of the follow symptoms, which indicate an allergic response or other complications:

Difficulty breathingA rapid heart rateA swollen throat, arms, or legsDizziness or a sharp drop in blood pressure (4,5)

Otherwise, wash the stings with soap and water and apply ice to keep the swelling down. You can use OTC pain or hydrocortisone creams as needed (6), but don’t apply rubbing alcohol — which can make the sting more painful. If you notice the sting continuing to swell or grow larger a day or two after you’re stung, that may be a sign of a secondary infection. Fever, muscle aches, or flu-like symptoms can also be cause for concern, and you should call your doctor.

Red Harvester Ant Stings

Harvester ants are less common today than they once were. They tend to live mostly in the Southwest and Texas. But because of their large size — usually one-quarter to one-half inch in length — they’re still a popular choice for ant farms. (7) Like fire ants, they sting rather than bite. But unlike fire ants, they’re reluctant to attack. A red harvester ant’s sting often feels and looks like a bee sting. A painful, swollen, red welt may form, which may itch after a few days and could take a week or more to go away.

Carpenter Ant Bites

Carpenter ants don’t sting — they bite. But when confronted by people, they tend to try to escape — not to swarm and attack. (8) If they do bite, the result and possible complications are similar to the stings of harvester ants. That is, the victim may experience a stab of pain and a red welt. (9) Both carpenter ants and red harvester ants are venomous, so their bite or sting can cause serious reactions. If you notice any signs of an allergic reaction or serious complication — problems breathing, a racing heart, flu-like symptoms — head to the emergency room. And again, if you notice any pronged swelling or flu-like symptoms — both of which could indicate a secondary bacterial infection — call your doctor. RELATED: Everything You Need to Know About Allergies Carpenter ants, on the other hand, show up inside homes and other wooden structures. They tend to bite only if handled or touched — for instance, if a person tries to squash them or swipe them away. Use sprays or other forms of pest control if you stumble onto these wood-loving ants, and you shouldn’t have to worry much about being bitten.

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