An Overview of Inflammation

Types, Causes, Symptoms, Diagnosis, and Treatment

Inflammation is the immune system’s natural response to injury or illness. When you are injured or become sick, your white blood cells release inflammatory chemicals into the blood and affected tissues to protect the body from foreign invaders, such as bacteria and viruses. The chemical release increases blood flow to the affected areas, causing redness and warmth. Some chemicals may leak into tissue and cause swelling. This protective process may also stimulate nerve endings, causing pain. 

While the inflammatory process is generally normal and natural, some diseases—like autoimmune arthritis—can cause the immune system to trigger an inflammatory response when there are no foreign substances to fight off. Your normally protective immune system turns against itself and starts to damage its own healthy tissues because it thinks those normal tissues are infected or abnormal. 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. 

Senior man having medical exam.
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Types and Their Causes

There are two types of inflammation: acute and chronic. 

Acute Inflammation 

Acute inflammation is commonly caused by trauma, harmful substances, or microbial invasion (i.e., bacteria and viruses). The healing process starts as soon as the body responds by releasing cytokines—proteins that promote inflammation. The acute inflammation process is rapid, may be severe, and occurs over a short period of time. Signs and symptoms may be present for a few days but may occur for longer in more serious causes. 

Examples of conditions and diseases that provoke acute inflammation are: 

Chronic Inflammation 

Chronic inflammation is long-term inflammation lasting for months or years. Chronic inflammation is usually caused by an autoimmune disorder, a disease in which the immune system attacks its own healthy tissues because it thinks they are diseased. Chronic inflammation can also be caused by low-level exposure to irritants, such as industrial chemicals, over long periods, or failure to cure whatever caused an acute inflammation, such as is the case with illness or infection.  

Numerous diseases are known for causing chronic inflammation. Examples include:


The symptoms of inflammation will depend on whether inflammation is acute or chronic.  

Acute Inflammation 

Acute inflammation tends to cause five specific symptoms—called cardinal signs— which are usually localized. These include: 

  • Redness: Redness occurs because blood vessels in the area are filled with more blood than usual.
  • Heat: With more blood flow to the affected area, the area becomes warm to the touch.
  • Swelling: Fluid buildup causes swelling.
  • Pain: The inflamed area is likely to be painful, especially with touch. This is because the chemicals released during the inflammatory process stimulate nerves and make them more sensitive.
  • Loss of function: There may be some loss of function in the affected area. Examples include not being able to move an inflamed joint or struggling with breathing if you have a respiratory infection. 

Acute inflammation does not always cause all five signs. Inflammation can also be silent and not cause any symptoms. 

Chronic Inflammation 

Symptoms of chronic inflammation tend to present differently than acute cases. 

Symptoms may include: 

  • Fatigue
  • Chest pain
  • Abdominal pain
  • Fever
  • Rash
  • Muscle pain
  • Joint pain
  • Mouth sores  

Chronic inflammation is dangerous because the body’s overactive inflammatory response will eventually start to damage healthy cells, tissues, and organs, eventually resulting in disability and life-threatening complications depending on the body part affected.

Research suggests chronic inflammation may cause a range of conditions from cancers to inflammatory arthritis. It has been estimated up to 15% of human cancers are related to chronic inflammation.


Inflammation—whether acute or chronic—can hurt. A person may feel pain, stiffness, distress, and discomfort, depending on the severity of the inflammation. The types of pain experienced vary but may be described as throbbing, pulsating, stabbing, pitching, burning, constant, and steady. 

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 them to enhance pain. 

Inflammatory Diseases 

In some diseases, the inflammatory process can be triggered even when there are no foreign invaders. In autoimmune diseases, the body's normally protective immune system damages its own tissues, as it mistakenly recognizes them as foreign or abnormal. 

Autoimmune Diseases 

There are more than 80 different autoimmune diseases. Researchers don’t actually know what causes autoimmune disease, but they suspect genetics, diet, infections, and chemical exposure might be involved. In response to unknown triggers, the immune system begins producing proteins that promote inflammation and attack the body’s own healthy issues. Treatment for autoimmune diseases generally focuses on reducing the overactivity of the immune system. 

Examples of autoimmune diseases include: 

Inflammatory Autoimmune Arthritis 

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

Increasing inflammation is the driving force behind inflammatory arthritis. In some types of inflammatory arthritis, such as RA, that same inflammation can affect the organs. Research shows inflammation is a key element in inflammatory disease progression that results in organ disease.

Symptoms of organ involvement depend on the particular organ affected. For example:

  • Inflammation of the heart (myocarditis) can cause shortness of breath or fluid retention.
  • Inflammation of the kidneys (nephritis) may cause kidney failure or high blood pressure.
  • Inflammation of the large intestine, known as colitis, may cause cramps and diarrhea.
  • Inflammation from autoimmune arthritis—especially RA—raises the risk for cardiac death.

Pain is not a primary symptom of organ involvement, because most organs do not have pain-sensitive nerves. Therefore, treatment for inflammatory diseases is aimed at reducing inflammation throughout the body to prevent organ involvement complications.

Diagnosing Inflammatory Diseases 

There is no one test that can diagnose inflammation or the conditions that cause it. Instead, based on your symptoms, your doctor will make a determination on what tests may be needed.  

Inflammatory conditions are usually diagnosed by taking a complete medical history and physical examination, which may include determining patterns of inflammation and whether joints are involved, evidence of morning stiffness, and evaluation of other symptoms. Your doctor may also request blood work and imaging studies. 


Blood testing can show inflammatory markers that indicate inflammation is in the body. However, these markers are not specific, since abnormal levels can exist without pinpointing a particular condition.

Tests your doctor may request include: 

  • C-reactive protein (CRP): CRP is a protein naturally produced in the liver in response to inflammation. High levels of CRP occur in inflammatory conditions. However, CRP can be elevated in both acute and chronic inflammation. Therefore, your doctor will rely on certain symptoms in addition to high levels of CRP in determining a diagnosis.
  • Erythrocyte sedimentation rate (ESR): ESR testing is usually done to identify inflammation is occurring. However, it is not used alone in making a diagnosis.
  • Plasma viscosity: This test measures the blood thickness. Inflammation thickens plasma. 

If your doctor thinks inflammation is the result of bacteria or a virus, he or she may perform other specific tests. You doctor will let you know what additional testing is needed and what he or she is looking for. 


X-ray, magnetic resonance imaging (MRI), and ultrasound are imaging tests used to diagnose and monitor autoimmune arthritis conditions. Imaging will look for signs of inflammation, bone erosion, tissue damage, and joint deterioration.


When inflammation is related to the healing process, reducing inflammation is helpful, but it is not always necessary. However, if inflammation is due to an autoimmune disease, treatment will depend on the specific disease and the severity of symptoms.  

General Inflammation 

For general inflammation, your doctor may recommend: 

  • Nonsteroidal anti-inflammatory drugs (NSAIDs): NSAIDs are usually a first-line treatment for short-term pain and inflammation. Most of these medications are available over the counter and include aspirin, ibuprofen, and naproxen. Your doctor can also prescribe prescription-strength NSAIDs for certain inflammatory conditions. NSAIDs are usually very effective, but can cause problems in the long term, including gastrointestinal bleeding.
  • 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 pain relievers: Topical analgesics can help with acute and chronic pain 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. Your doctor can also prescribe prescription-strength versions. 

Inflammatory Diseases 

Treatment for inflammatory conditions, including autoimmune arthritis, includes medications, rest, exercise, and surgery to correct joint damage. The type of treatment is dependent on the type of disease, a person's age and overall health, and severity of symptoms.  

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

Because medications to treat inflammatory diseases cause harsh side effects, it is important to see your doctor regularly. 

A Word From Verywell

While inflammation is a normal immune system response, long-term inflammation can be damaging and associated with autoimmune disorders. If you are experiencing long-term inflammation, make an appointment with your doctor. He or she can run some tests and review your symptoms to see if you need treatment for an underlying medical condition. 

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