Ask the Doctors: What to do about fire ant bites?

Dear Doctors: My husband and I were clearing weeds when I felt a sharp jab on my leg. It was a bite from a fire ant. The pain was severe, as was the reaction. I got a huge lump, blisters and bright red skin. What can you do for fire ant bites?

Answer: First a little background. Fire ants are native to South America. More than a century ago, the first of the two species now found in the United States arrived aboard a cargo ship in Mobile, Alabama. Black fire ants arrived in 1918. Red fire ants, also shipboard stowaways, were first observed in the late 1930s.

Fire ants largely inhabit the Southeast and Southwest, California and lower Oregon, so be careful if you travel to these areas. They spread by expanding their colonies and being introduced in transported agricultural products.

Both species are extremely aggressive when disturbed. Touch or kick a nest, and the ants respond by stinging, often multiple times. They fasten themselves to the skin by clamping down with powerful jaws, then inject a painful venom via a stinger on their hind end.

The venom can prompt a strong, prolonged immune response. Though this is rare, if you’re allergic to the bites, they can be life-threatening.

The initial pain of the bite is followed by a painful burning sensation from the venom, which gives the ants their name. The area around the bite quickly becomes inflamed, dotted with itchy red bumps. Within a day, the bumps develop into fluid-filled blisters.

Because a single fire ant can bite and sting multiple times, anyone who’s bitten should immediately and briskly rub the ants off the skin and get away fast from the ants. Then, wash the area.

Over-the-counter antihistamines can blunt the initial effects of the bite. Hydrocortisone cream and ice packs can ease pain and swelling, which usually s localized to the bite and goes away in a few days. If symptoms don’t respond to over-the-counter medications, a doctor might advise prescription-strength versions.

The pustules formed around a fire ant bite last a week or more. Infection is possible, so care for them as you would any wound. Keep the area protected, clean and free of dirt.

If you develop a severe allergic reaction, seek immediate attention. Symptoms include noisy or labored breathing, excessive sweating, nausea, hives or welts, dizziness, unusual weakness, swelling of the face or eyes, slurred speech or chest pain.

Dr. Eve Glazier and Dr. Elizabeth Ko are UCLA Health internists.