When Oscar Brann imagined retirement, he pictured days spent fishing with his grandson, or doing yardwork at his home in Skowhegan, Maine.

But itchy and flaky red rashes appeared across his body a few years ago, making it excruciating to move, he said. The pain forced Brann, a 62-year-old former shoe manufacturer, to retire early. Instead of gardening in his backyard, he spent hours on the couch, trying to find relief.

“The skin that came off my feet, it was just unbelievable,” Brann said. “I had to sweep my floor every day.”

Brann, who still copes with the debilitating rashes, is among millions of people with eczema, a broad term for a group of skin conditions that affects about 10% of the U.S. population. The most common form of eczema is atopic dermatitis, and the terms are often used interchangeably.

The condition often crops up during childhood, experts said. And while some people outgrow it, atopic dermatitis can last into adulthood, or appear later in life.

Sometimes, the rashes are an itchy nuisance that flare up once in a while. But that’s not always the case, said Dr. Brittany Craiglow, an adjunct associate professor of dermatology at the Yale School of Medicine. When it’s severe, “it can be dramatically life altering,” she said.

What does it look like?

Atopic dermatitis can appear differently on different people. Someone with darker skin might have brown, purple or gray rashes, while the rashes might look pink or red on lighter skin. Regardless, dry, itchy rashes are a hallmark of the condition, and other signs include oozing and thickened or scaly skin, experts said.

These patches of irritated skin can show up anywhere, said Dr. JiaDe Yu, director of the Atopic Dermatitis Clinic at Massachusetts General Hospital, but they often appear on inner elbows, behind the knees, and on the hands, feet and neck.

The condition has invisible signs too, experts said. For instance, people with severe atopic dermatitis often struggle to sleep, or focus at work or school, and may be more likely to develop anxiety or depression.

“This isn’t so much a ‘life or death’ disease,” Craiglow said, “but it’s a quality of life disease.”

What causes it, and why?

It’s not completely clear what causes atopic dermatitis, but there are several factors in play, experts said.

Everyone with the condition has a weakened or damaged skin barrier, the outermost layer of skin, said Dr. Shari Lipner, an associate professor of clinical dermatology at the Weill Cornell Medical Center in New York City.

Think of the skin barrier as like a brick wall, Yu said: Skin cells are the bricks, and they’re held together by a mortar made primarily of fatty substances. When someone has atopic dermatitis, the barrier is “leaky,” said Dr. Joy Wan, an assistant professor of dermatology at Johns Hopkins University. “It’s almost like there’s little holes in it,” Lipner added, making it easier for irritants to get in and for moisture to escape, causing dry, itchy and inflamed skin.

There are several reasons someone might have a leaky skin barrier, and develop atopic dermatitis. For one, their genes: The condition tends to run in families, and this, in part, is because those with a genetic predisposition for atopic dermatitis may have less filaggrin, a protein that keeps the skin barrier strong, Yu said.

People with atopic dermatitis are also more likely to have an overactive immune response, making them more sensitive to normally harmless substances like the fragrances or preservatives found in personal care products, Yu said. This response causes their white blood cells to release too many cytokines — a type of protein that can trigger skin inflammation.

People with the condition might also have a less diverse skin microbiome than those without it, Wan said. This means they have an “undergrowth of certain healthy bacteria” and an “overgrowth of pro-inflammatory bacteria,” Yu said, which can cause symptoms to set in, or further aggravate them.

How can I manage it?

There isn’t a cure for atopic dermatitis, but there are ways to manage mild symptoms at home, experts said.

Moisturize. Moisturizing your skin protects its barrier and minimizes flare-ups. Consider thick ointments and creams made with petroleum jelly, which are more effective than thinner lotions, experts said. Check the ingredients label for other moisturizing ingredients like ceramides, glycerin and dimethicone, Craiglow said, but avoid plant extracts such as chamomile, Yu added, which can make atopic dermatitis worse. “Bland is best when you have eczema,” Craiglow said.

Take short showers. Long hot showers and baths dry out the skin, Craiglow said. Use lukewarm water, and limit bathing to 10 minutes or fewer. Afterward, moisturize skin while it’s still damp to lock in hydration.

Use anti-itch cream. One percent hydrocortisone cream is a mild, over-the-counter topical steroid that can help with less severe flare-ups, experts said. Follow the instructions on the label. If after a week it has proved ineffective, stop using it and consider visiting a dermatologist.

Dermatologists may prescribe stronger topical creams, pills, injectable medications or phototherapy to manage severe atopic dermatitis, experts said. No treatment option is perfectly effective for everyone, Yu said, but since medications were first developed for the condition decades ago, “we’ve come a long way.”