Inflammation is a familiar word. We've seen it defined as a symptom or risk factor for disease, the body's response to injury, a side effect of medication, or even a class of medication, called anti-inflammatories. But what exactly does inflammation mean?
Inflammation is when part of the body becomes red, irritated, swollen, or painful. This can happen when the body is fighting an infection from bacteria or viruses or in response to an injury. While inflammation can be uncomfortable, it's also a good sign because the body is trying to protect and heal itself.
What causes the signs and symptoms of inflammation?
A stye (a bacterial infection of the eyelid's oil glands), for example, causes a painful, red, swollen lump to appear on the eyelid, like the woman pictured above. The cause of this lump is what’s called the inflammatory process. Bacteria invade the oil gland and begin the inflammatory process. The body's immune system identifies the invading bacteria and sends its first responders (the white blood cells) to the infection site. The white blood cells surround and secure the infection, much like a crime scene cordoned off with yellow tape. Their job is to contain the damage, kill the bacteria, and repair the tissue. This entire process causes inflammation, which includes these symptoms:
The warmth and redness are caused by the increased blood flow to the area. The swelling is caused by an accumulation of fluid at the wound/infection site, and in this case, the fluid inside the stye is pus. The inflammatory process stimulates the nerve endings in the area, which is why we feel pain. This kind of inflammation—called acute inflammation—is the normal, protective response of a healthy immune system. The other type is long-term, misdirected, and unresolved—this is known as chronic inflammation.
Most chronic inflammation is caused by autoimmune disease. This is when the body's immune system can't tell the difference between healthy cells and threatening germs, like viruses or bacteria. The body then attacks its own healthy tissues. Chronic inflammatory disease that affect the eyes include: