Aging can bring unwelcome surprises, like crusty brown spots that gradually appear on your face, neck or trunk.

They’re called unflattering names: age spots, barnacles or, God help us, senile warts, but physicians know them as seborrheic keratosis lesions, or SK lesions, for short. They come in as many varieties as apples at a farmers’ market: waxy, warty, raised or flat. The good news is they’re benign.

Of course, that doesn’t stop many of the 83 million Americans who have them from complaining. Sometimes the lesions itch, bleed or get irritated by a belt or a bra strap, but for the most part, they’re simply an unwelcome reminder that there’s much in life that’s out of our control.

And there hasn’t been an easy cosmetic treatment, until now.

On Dec. 14, the Food and Drug Administration approved a first-of-its-kind liquid called Eskata that targets these unsightly spots. By late April, people who have the means and the patience to sit through at least two visits to their dermatologist’s office can get rid of some raised spots.

“A lot of patients have SKs and want them gone,” said Ellen Marmur, a dermatologist with two Manhattan practices who wasn’t part of the clinical trials conducted by Aclaris Therapeutics, the maker of Eskata. She thinks it has the potential to be a “great tool” in carefully selected patients.

Some people have one or two spots. Others have dozens across their chest and back. “The sheer number of lesions can be depressing,” said Victor Neel, the director of dermatologic surgery at Massachusetts General Hospital, adding that he has heard people say “they haven’t taken off their shirt at the beach in 25 years.”

Before Eskata, dermatologists could freeze lesions or use a laser or scalpel to remove them, but the procedures could be painful, and patients didn’t necessarily want to risk potential scarring for a cosmetic annoyance.

Here’s how Eskata works: After a dermatologist has determined a spot is not cancer, a staff person (not necessarily a doctor) delicately applies the highly concentrated hydrogen peroxide liquid to each lesion four times, roughly a minute apart. The idea is to moisten the lesion to dissolve it, while avoiding damaging surrounding skin.

Noelle Galperin, 49, a strategy consultant in Miami who participated in a clinical trial at Leslie Baumann’s office, said she felt a “tingling, almost burning, sensation.” Later, scabs formed on her lesions, and she wore an adhesive bandage for a few weeks to hide the spots from the sun.

Galperin used to be so self-conscious about the lesion on her forehead that she would edit it out of pictures. “Who wants to be seen with brown age spots?” she said.

She also wanted two larger spots on her back treated so “there’s no chance of seeing them in my wedding dress,” said Galperin, who will marry soon in France in a gown with a V-shaped back in scalloped lace. One is gone, but the other, she said, will need another treatment to remove it completely.

“Patients need to know that there’s a chance after two treatments their lesion may be gone and they’ll be happy,” said Robert T. Brodell, the chairman of the department of dermatology at the University of Mississippi Medical Center in Jackson. “Or some may have a lesion that’s 90 percent better, or some might take a third touch-up treatment.”

Still, Brodell called Eskata “something that’s totally different that’s an advance.”

In one study, approximately 65 percent of the facial lesions on roughly 220 patients were completely or almost clear 106 days after the first treatment, compared with 15 percent of roughly 225 patients who got a placebo liquid.

In another study, about 50 percent of SKs treated with Eskata in the trial were assessed as clear or near clear, according to Neal Walker, a dermatologist and the chief executive of Aclaris Therapeutics.

Walker estimated that each Eskata applicator will cost the patient $200 to $250. One applicator, he estimated, will be able to treat seven large spots up to 1.5 centimeters wide, or 10 smaller ones.

Neel is starting a company to bring to market his own topical treatment for SKs, one that would theoretically work by inhibiting an enzyme that the lesions need for survival. The lesion would die, but the regular skin wouldn’t be damaged, so large areas of skin could be treated quickly. But that is years off.

Some research has found that Eskata has minimal side effects when carefully applied. More than 90 percent of the patients had no scarring or pigmentation issues. But darker skin tends to have more trouble with pigmentation and scarring after, say, cryotherapy. Ninety-eight percent of patients in the clinical trials were Caucasian. “It’s a huge gap in the study design,” Marmur said.