Inflammation is the body’s protective response to harmful stimuli like pathogens, damaged cells, or irritants. This fundamental mechanism of the innate immune system eliminates the initial cause of cell injury, clears damaged tissues, and initiates repair. A normal inflammatory response helps the body heal from injury or infection.
What Causes Inflammation to Begin?
Inflammation begins when the body’s immune system detects a threat or damage. Physical injuries, such as cuts, burns, or sprains, are common triggers.
Infections from bacteria, viruses, or fungi also activate the inflammatory process. For instance, a bacterial infection like strep throat or a viral illness such as the flu can cause localized inflammation.
Allergens, like pollen or certain foods, can provoke inflammation in sensitive individuals. Similarly, irritants such as chemicals, pollutants, or foreign objects like a splinter can trigger inflammation.
Autoimmune conditions represent another category of triggers where the immune system mistakenly attacks healthy body tissues. In diseases like rheumatoid arthritis or lupus, this misdirected attack leads to ongoing inflammation and tissue damage.
How the Body Responds
Once inflammation is triggered, a brief constriction of blood vessels occurs, followed by prolonged dilation of arterioles and capillaries in the affected area. This vasodilation increases blood flow, bringing more immune cells and healing factors to the site, leading to localized redness and warmth.
Increased blood flow also increases the permeability of capillaries, particularly venules. This allows fluid, plasma proteins, and immune cells to leak out of the bloodstream and accumulate in the extravascular space. The leakage of fluid into the tissues causes swelling, which can put pressure on nerve endings and result in pain.
Immune cells, primarily white blood cells like neutrophils and later macrophages, migrate from the blood vessels to the site of injury or infection. This involves cells adhering to the inner lining of blood vessels and squeezing through gaps between endothelial cells. Once in the tissue, these cells clear debris, engulf pathogens, and remove damaged cells.
Different Types of Inflammatory Responses
Inflammation manifests as acute or chronic. Acute inflammation is the body’s immediate, short-term response to sudden injury or infection. It typically resolves within hours to a few days once the threat is eliminated.
Examples of acute inflammation include swelling and pain from a sprained ankle, redness and heat around a cut, or symptoms of a common cold or strep throat. This type of inflammation aids in healing and protection.
Chronic inflammation, in contrast, is a prolonged response that can last for months or even years. It occurs if the initial trigger persists, or if the immune system continues to respond without a threat, as seen in autoimmune diseases. Unlike acute inflammation, chronic inflammation can cause ongoing damage to healthy tissues and organs.
While acute inflammation is a necessary part of the body’s defense, chronic inflammation can have detrimental long-term implications. It is associated with various health conditions, as persistent immune activity can break down healthy tissue.