Inflammation is caused by your immune system releasing defensive cells and chemicals into your tissues or bloodstream. In the short term, this response is protective, triggered by injuries, infections, and toxins. But when the same response keeps firing without a real threat, it becomes chronic inflammation, a slow-burning process linked to heart disease, diabetes, depression, and autoimmune conditions. The causes of chronic inflammation range from what you eat and how you sleep to the air you breathe and the stress you carry.
How Acute Inflammation Differs From Chronic
Acute inflammation is your body’s emergency response. When you cut your finger, break a bone, or catch the flu, immune cells rush to the site of damage to contain the threat and begin repairs. The redness, swelling, heat, and pain you feel are signs this system is working. Bacterial infections like strep throat, viral infections like influenza, and physical trauma all trigger it. This type of inflammation is short-lived, typically resolving in days to weeks once the threat is gone.
Chronic inflammation is a fundamentally different problem. Instead of shutting off, your immune system continues sending inflammatory cells even when there’s no injury or invader to fight. Over months and years, those cells damage healthy tissue. This is the type of inflammation behind conditions like rheumatoid arthritis, atherosclerosis, type 2 diabetes, and certain cancers. Because it often produces no obvious symptoms early on, it can progress silently for a long time.
Dietary Triggers
What you eat has a direct effect on your body’s inflammatory activity. Diets high in refined sugar and processed carbohydrates raise blood glucose levels in ways that activate a key inflammatory switch inside your cells. High glucose triggers a chain of chemical modifications that sustain the production of inflammatory signaling molecules, particularly one called TNF-alpha, which acts like an alarm bell that keeps other immune cells on high alert. The result is a persistent low-grade inflammatory state that develops gradually with years of poor dietary patterns.
Trans fats, highly processed vegetable oils, and excess alcohol follow similar patterns, promoting the release of inflammatory chemicals. On the flip side, diets rich in vegetables, fatty fish, nuts, and whole grains tend to lower these same markers. The effect isn’t instant in either direction. It’s the long-term pattern of eating that shifts your baseline level of inflammation up or down.
Chronic Stress and Cortisol Resistance
Your body uses the hormone cortisol as a natural brake on inflammation. Under normal circumstances, a stressful event triggers cortisol release, which keeps your immune response in check so it doesn’t overreact. But when stress becomes chronic, something breaks in this feedback loop. Your immune cells gradually stop responding to cortisol’s “calm down” signal, a phenomenon researchers call glucocorticoid receptor resistance.
A study published in the Proceedings of the National Academy of Sciences described this mechanism directly: prolonged stress causes immune cells to become resistant to cortisol, which in turn prevents the body from properly regulating inflammation. With the brake pedal no longer working, inflammatory activity runs unchecked. This helps explain why people under chronic psychological stress, whether from caregiving, financial hardship, or ongoing conflict, show elevated inflammatory markers and higher rates of inflammatory diseases.
Your Gut Lining Plays a Surprising Role
Your intestines are lined with a single layer of cells that acts as a selective barrier, letting nutrients through while keeping bacteria and their byproducts confined to the gut. When that barrier is compromised, fragments of bacterial cell walls (called lipopolysaccharides) can slip into the bloodstream. Once there, they bind to receptors on immune cells and trigger a bodywide inflammatory response.
Stress is one of the clearest disruptors of this barrier. During periods of chronic stress, immune cells in the gut wall release chemicals that damage the protective mucus layer and loosen the junctions between intestinal cells. The population of beneficial gut bacteria also shifts, with overall diversity declining. The combination of a thinner mucus layer, fewer protective bacteria, and weakened cell-to-cell connections allows bacterial products to “leak” into the body’s interior. This process has been linked not only to digestive inflammation but also to neuroinflammation, with downstream effects on mood and mental health.
Sleep Loss Disrupts Inflammatory Rhythms
Your body’s inflammatory signaling follows a circadian rhythm. One key inflammatory molecule, IL-6, normally peaks twice in a 24-hour cycle (around 5 a.m. and 7 p.m.) and drops to its lowest levels around 8 a.m. and 9 p.m. Sleep deprivation doesn’t necessarily increase the total amount of IL-6 your body produces, but it scrambles the timing. After a night of lost sleep, daytime levels of IL-6 rise significantly while nighttime levels drop.
That daytime spike is part of why sleep-deprived people feel exhausted and foggy: elevated inflammatory signaling during waking hours contributes directly to fatigue. Research has also shown that the less sleep people get at baseline, the higher their overall daytime inflammatory activity tends to be. This creates a vicious cycle where poor sleep raises inflammation, and inflammation in turn makes it harder to sleep well.
Air Pollution and Environmental Toxins
Inhaled air pollution, particularly fine particulate matter from vehicle exhaust, industrial emissions, and wildfire smoke, is a potent inflammatory trigger. These tiny particles are small enough to penetrate deep into the lungs and even cross the air-blood barrier into circulation. Once lodged in the lungs, they activate immune cells called macrophages, which respond by pumping out a cascade of inflammatory chemicals including IL-6, TNF-alpha, and several others.
The inflammation doesn’t stay local. Particulate matter deposited in the smallest air sacs of the lungs generates enough of a local immune response to shift the entire body into a more inflammatory state. This systemic inflammation accelerates blood clotting, promotes plaque formation in arteries, and raises the risk of heart attack and stroke. It’s a major reason why cardiovascular disease rates are consistently higher in cities with poor air quality, even after accounting for diet, exercise, and smoking.
Autoimmune Triggers
In autoimmune diseases, the immune system mistakes the body’s own tissues for a threat and mounts a sustained inflammatory attack against them. One well-understood mechanism behind this is molecular mimicry: a protein on the surface of a bacterium or virus closely resembles a protein in your own tissue. After the immune system builds a defense against the infection, those same antibodies or immune cells accidentally target healthy cells that look similar.
Rheumatic fever is a classic example. After an infection with group A streptococcus (the bacterium behind strep throat), some people develop antibodies that cross-react with proteins in the heart, joints, brain, and skin. The same principle of mistaken identity has been implicated in multiple sclerosis, where immune cells attack the insulating layer around nerves, and in type 1 diabetes, where they destroy insulin-producing cells in the pancreas. In each case, the inflammation is real and damaging, but there’s no external threat left to fight.
Excess Body Fat
Fat tissue isn’t an inert storage depot. It’s an active endocrine organ that produces its own inflammatory signaling molecules. The more excess fat your body carries, particularly visceral fat stored around internal organs, the more of these signals it releases into the bloodstream. This creates a baseline of chronic, low-grade inflammation that persists as long as the excess fat is present.
Visceral fat is especially problematic because of its proximity to the liver and other organs involved in metabolism. The inflammatory chemicals it produces interfere with insulin signaling, promote arterial plaque buildup, and keep the immune system in a state of constant mild activation. Weight loss, even modest amounts in the range of 5 to 10 percent of body weight, has been shown to measurably reduce circulating inflammatory markers.
How Chronic Inflammation Is Measured
The most commonly used blood test for systemic inflammation is high-sensitivity C-reactive protein (hs-CRP). The American Heart Association and the CDC established clinical cutoffs: levels below 1 mg/L indicate low risk, 1 to 3 mg/L moderate risk, and 3 mg/L or above high risk for cardiovascular problems. Readings above 10 mg/L often reflect an acute infection or injury rather than the chronic, smoldering inflammation linked to long-term disease, so doctors typically repeat the test to confirm.
hs-CRP is useful but nonspecific. It tells you inflammation is present somewhere in the body without pointing to the cause. Other markers like IL-6, fibrinogen, and erythrocyte sedimentation rate can provide additional context. No single blood test paints the full picture, which is why doctors interpret inflammatory markers alongside symptoms, medical history, and other lab results.