Georgie Henley from 'The Chronicles of Narnia' almost lost her arm to a 'flesh-eating' bacteria but 'grueling' surgery saved it. Here's what to know about necrotizing fasciitis.

• Georgie Henley of "The Chronicles of Narnia" caught a "flesh-eating" bacteria when she was 18.
• The actor, who played Lucy, said she hid her surgery scars for the last nine years.

"The Chronicles of Narnia" actor Georgie Henley almost lost her left arm after catching a "flesh-eating" bacteria when she was 18, and had "grueling" surgery to prevent it from being amputated.

Writing in a Instagram post on Tuesday, Henley — who played Lucy in "The Chronicles of Narnia" film series — said that she developed what is known as necrotizing fasciitis while she was at university and that it "wrought havoc" throughout her body.

Commonly known as "flesh-eating" disease, necrotizing fasciitis is a rare bacterial infection that can progress quickly. It kills 20% of people that get it, according to research. The treatment is strong antibiotics and emergency surgery to cut away the dead tissue.

"In order to prevent the amputation of my left hand and arm I received grueling invasive surgery, and later extensive reconstructive surgery," she wrote.

Henley said that the surgery left her with scars, which she hid from the entertainment industry for the last nine years. She covered them with make-up, long sleeves, and bandages on sets and stages, and wore trousers so she could put the affected hand in a pocket for photographs.

"I worried that my scars would prevent me from getting work," she said.

Henley said that she was no longer ashamed of her scars and felt proud to have visible scars in the industry.

"They are a map of the pain my body has endured, and most importantly a reminder of my survival. They do not affect my capacity as an actor," she wrote.

Necrotizing fasciitis can happen when bacteria enter the body through breaks in the skin

Henley did not reveal how she caught the infection.

According to the Centers for Disease Control and Prevention, the various bacteria that cause the illness can enter the body through breaks in the skin, for example insect bites, cuts, or burns. However necrotizing fasciitis can also occur after blunt injuries too, when there is no break in the skin.

Anyone can catch it, but most people that get it have another health condition that weakens their immune system. It's "very rare" to catch the infection from another person, the CDC states.

Symptoms like an area of red skin can often be 'confusing'

According to the CDC, necrotizing fasciitis initially causes symptoms like a red, warm, or swollen area of skin that spreads quickly, severe pain that extends beyond the area that's red or swollen, and fevers.

Later symptoms include: ulcers, blisters, black spots on the skin, changes to skin color, pus or oozing from the affected area, dizziness, tiredness, and nausea.

Those symptoms, which are similar to other minor illnesses, can often be "confusing" and develop quickly, but people that get them should seek medical attention straight away, it states.

Henley didn't detail the symptoms that she experienced from the condition, but wrote that she would talk more about her experiences in the future.

"Today I am simply happy to feel, for the first time in a very long time, finally free," she wrote.