What Is Inflammation?

Types, Causes, Symptoms, Diagnosis, and Treatment

Inflammation is the immune system’s natural response to injury and illness. Inflammatory chemicals in the bloodstream work to protect your body from foreign invaders like bacteria and viruses. When you are injured, a localized inflammatory response plays a critical role in the healing process.

There are two types of inflammation, acute and chronic. You can think of acute inflammation as the "good" kind because it helps us heal, while chronic inflammation is the "bad" kind because of its association with chronic disease. Research has shown that chronic inflammation plays a role in several health conditions, including arthritis, heart disease, type 2 diabetes, cancer, and Alzheimer's disease.

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Types of Inflammation

Acute and chronic inflammation have different causes, symptoms, and purposes.

Acute Inflammation

Acute inflammation is typically caused by injuries, like a sprained ankle, or by illnesses, like bacterial infections and common viruses. The acute inflammation process happens quickly and can be severe. If you've ever broken a bone or cut yourself, you've seen inflammation in action. Common signs of inflammation following an injury include:

  • Redness
  • Pain and tenderness
  • Swelling, bumps, or puffiness
  • Warmth at the injury site
  • Bruising
  • Stiffness
  • Loss of mobility

Depending on the cause and severity of the wound, acute inflammation can last anywhere from a few days to a few months.

Sometimes acute inflammation is localized to one area and sometimes it is systemic, as with a viral infection. When your body identifies a harmful invader, such as a bacteria or virus, it initiates a whole-body immune response to fight it off. White blood cells trigger the release of several inflammatory chemicals. This type of acute inflammation causes you to feel sick and exhausted, as your body puts all its energy toward fighting off infection.

Symptoms of this type of inflammation include:

  • Fever
  • Nausea
  • Lethargy
  • Sleepiness
  • Irritability
  • Runny nose
  • Sore throat
  • Stuffy nose
  • Headache

Signs and symptoms may be present for a few days or weeks, or possibly longer in more serious causes.

Some acute infections are caused by more localized inflammation. Like most conditions caused by inflammation, they tend to end in "-itis."

Examples include:

Chronic Inflammation

Chronic, long-term inflammation can last for years or even an entire lifetime. It often begins when there is no injury or illness present and lasts far longer than it should. Scientists don't know why chronic inflammation happens, as it doesn't seem to serve a purpose like acute inflammation. But they do know that over time it can cause major changes to the body's tissues, organs, and cells.

Research has found an association between chronic inflammation and a wide variety of serious conditions. Keep in mind that there is a major difference between two things being associated and one thing causing another. Chronic inflammation is one of several contributing factors in disease onset and progression. So far, the strongest link between chronic inflammation and disease has been seen in type 2 diabetes and heart disease.

Other conditions associated with chronic inflammation include:

Chronic inflammation often progresses quietly, with few independent symptoms. Despite its subtlety, chronic inflammation represents a major threat to the health and longevity of a large population of individuals.

What Causes Chronic Inflammation

Researchers have identified several common causes of chronic systemic inflammation, many of which are closely associated with modern living and aging. Causes of chronic inflammation include:

  • Physical inactivity. An anti-inflammatory chemical process occurs in the bloodstream when your muscles are in motion. People who don't meet the minimum activity recommendations for optimal health (about half of all American adults) have an increased risk of age-related diseases.
  • Obesity. Fat tissue, especially visceral fat (a deep layer of fat around the abdominal organs), actually produces pro-inflammatory chemicals.
  • Diet. Diets high in saturated fat, trans-fat, and refined sugar are associated with increased inflammation, especially in overweight people.
  • Smoking. Smoking cigarettes lowers the production of anti-inflammatory molecules and increases inflammation.
  • Low sex hormones. Sex hormones like estrogen and testosterone suppress inflammation. Lower levels of these hormones, common in advanced age, increase the risk of inflammatory diseases.
  • Stress. Psychological stress is associated with increased inflammation.
  • Sleep disorders. People with irregular sleep schedules have more markers of inflammation than people who get a regular eight hours a night.
  • Age. Research shows that chronic inflammation gets worse as we age.

A large study of more than 20,000 seniors found that those meeting the minimum weekly activity requirements had a 40% lower risk of Alzheimer's disease compared to their inactive counterparts. There are several potential reasons for this finding, but reduced inflammation likely plays a role.

Autoimmune Diseases

In some diseases, the inflammatory process can be triggered even when there are no foreign invaders. In autoimmune diseases, the immune system attacks its own tissues, mistaking them as foreign or abnormal.

Researchers don’t know exactly what causes autoimmune disorders, but they suspect a combination of genetic and environmental factors. There are more than 80 different autoimmune diseases affecting different parts of the body. Inflammation caused by autoimmune disorders does different types of damage to different parts of the body.

Type 1 diabetes, for example, is an autoimmune disorder that happens after the body attacks the cells in the pancreas that produce insulin, leading to lifelong health consequences. Psoriasis, another autoimmune condition, involves inflammation of the skin that comes and goes throughout a lifetime.

Common autoimmune diseases include:

Some types of autoimmune arthritis—but not all—are the result of misdirected inflammation. Arthritis is a general term describing the inflammation of the joints. Some autoimmune diseases that cause joint inflammation are:

Treatment for autoimmune diseases varies but often focuses on reducing the overactivity of the immune system.

Why Inflammation Hurts

Inflammation—whether acute or chronic—can hurt. A person may feel pain, stiffness, distress, and discomfort, depending on the severity of the inflammation.

Inflammation causes pain because swelling pushes on sensitive nerve endings, sending pain signals to the brain. Additionally, some of the chemical processes of inflammation affect the behavior of nerves, causing enhanced pain sensation.

The increased number of cells and inflammatory substances may also enter joints, causing irritation, swelling of the joint lining, and eventual breakdown of cartilage—the smooth tissue covering the ends of bones where they come together to form joints.

Diagnosing Inflammation

There is no single test that can diagnose inflammation or the conditions that cause it. Instead, based on your symptoms, your healthcare provider will decide which tests may be needed. First, your healthcare provider will take a complete medical history and conduct a physical examination. Your healthcare provider may also request blood work and imaging studies.

Blood Tests

Blood tests can look for certain biological markers that indicate inflammation is present. However, these tests are considered informative rather than diagnostic. They help give your healthcare provider clues as to what's going on.

Tests your healthcare provider may request include:

  • C-reactive protein (CRP): CRP is a protein naturally produced in the liver in response to inflammation. High levels of CRP are common in people with chronic inflammation, inflammatory diseases, and acute inflammation.
  • Erythrocyte sedimentation rate (ESR): ESR testing is usually done to identify whether inflammation is occurring.


Imaging modalities that can detect inflammation include:

  • MRI with gadolinium enhancement
  • Ultrasound with power doppler
  • Nuclear imaging


Treatment will depend on the specific disease or ailment and the severity of symptoms.

Treatment for inflammatory diseases aims to reduce inflammation throughout the body to prevent serious complications.

Acute Inflammation

For general inflammation, your healthcare provider may recommend:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs): NSAIDs are usually the first-line treatment for short-term pain and inflammation. Most of these medications are available over the counter, including aspirin, ibuprofen, and naproxen. Your healthcare provider can also prescribe prescription-strength NSAIDs for certain inflammatory conditions.
  • Corticosteroids: This is a type of steroid commonly used to treat swelling and inflammation. Corticosteroids are available in pill form and as injections. These drugs are only prescribed for short periods, since they are known to cause serious side effects.
  • Topical medications: Topicals, including analgesics and steroids, can help with acute and chronic pain and inflammation of the skin and joints without the side effects of oral treatments. They are also helpful for managing long-term inflammation when they contain an NSAID, such as diclofenac or ibuprofen.

Chronic Inflammation

In addition to treating joint pain and inflammation, medications for inflammatory diseases can help to prevent or minimize disease progression. Medications may include:

Because many medications used to treat inflammatory diseases can cause harsh side effects, it is important to see your healthcare provider regularly.

Preventing Chronic Inflammation

There are a number of lifestyle changes you can make to prevent and reverse chronic inflammation, these include:

  • Losing weight
  • Eating a healthy diet rich in fruits, vegetables, whole grains, and lean proteins
  • Getting 150 minutes of moderate aerobic exercise per week (or 75 minutes of vigorous exercise)
  • Incorporate a muscle-strengthening activity at least twice a week
  • Quitting smoking
  • Spending less time sitting down
  • Walking more
  • Getting enough sleep
  • Employing stress reduction techniques like meditation or yoga
  • Avoiding isolation and connecting with others
  • Seeing your healthcare provider regularly

A Word From Verywell

While inflammation is a normal immune system response, long-term inflammation can be damaging. If you are at risk for long-term inflammation, make sure to schedule regular checkups with your healthcare provider. Your healthcare provider may suggest preventive lifestyle changes or they may start you on a new treatment plan.

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Article Sources
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