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What is inflammation? Causes, treatment, and prevention

This is your body’s first line of defense against injury or illness—but it can go wrong

If you’ve ever strained a muscle or come down with a case of the common cold, you’ve experienced inflammation; it’s your body’s first line of defense against injury, illness, and disease. But inflammation can also occur due to autoimmune disorders like Crohn’s disease, which causes the body to target and attack it’s own healthy tissues. No matter the cause, the inflammatory process triggers the release of white blood cells to the affected area in order to promote the healing process. This immune system response can cause an array of symptoms—most commonly pain and swelling. 

What is inflammation?

Inflammation is the body’s immune response to illness, injury, or foreign body. It often results in local redness, warmth, or swelling, or may cause a systemic response such as fever, body aches, or malaise. Inflammation protects the body against harm and also tells the brain and body that it needs to address an issue in order to maintain homeostasis, or a healthy state. “Inflammatory proteins are released to kick-start the immune response to rid the body of things like infections or treat an area of distress, say a swollen ankle or an injured heart after a heart attack,” says Anne Davidson, MBBS, professor in the Institute of Molecular Medicine at the Feinstein Institutes for Medical Research and rheumatologist in Manhasset, NY.

There are two types of inflammation: acute inflammation and chronic inflammation. The purpose of acute inflammation is to repair damage to the body, resulting in increased blood flow to the area. “Acute inflammation is caused by an injury—if you fall and sprain your ankle, your body sends factors to that area to help it heal,” explains Eric Ascher, DO, attending physician at Northwell Health, Family Medicine in New York. “Acute inflammation can also be related to getting sick with a virus or bacterial infection, like when you have the cold, the flu, bronchitis, a headache, or any sort of skin reaction.” 

Chronic inflammation causes harm to the body and can even lead to damaged tissue and the development of certain diseases. “Chronic inflammation is typically linked to a genetic disease, an autoimmune disease, sensitivity to an allergen, or exposure to an irritant over an extended period of time,” Dr. Ascher says. “It could be arthritis, different cancers, diabetes, heart disease, or genetic and autoimmune diseases such as lupus, psoriasis, and colitis.” 

Acute vs. chronic inflammation
Acute inflammation Chronic inflammation
Definition Acute inflammation is triggered by the body’s healing response, has a fast onset and is short-term. Chronic inflammation is ongoing, long-lasting  and can cause damage to healthy tissues.
Common causes
  • Injury
  • Bacterial infection
  • Viral infection
  • Allergens
  • Foreign bodies
  • Allergens
  • Cancer
  • Celiac disease
  • Diabetes
  • Heart disease
  • Obesity
  • Rheumatoid arthritis
  • Crohn’s disease
  • Lupus
  • Hashimoto’s thyroiditis
  • Interstitial lung diseases
  • Hepatitis C
  • Inflammatory bowel disease
  • Alzheimer’s disease
  • COVID-19
  • Pain
  • Swelling
  • Redness
  • Warmth
  • Loss of function
  • Joint swelling, tenderness, stiffness
  • Flu-like symptoms (fever, malaise, muscle aches)
  • Pain
  • General malaise
  • Fatigue
  • Bloating
  • Mental fogginess
  • Achy joints
  • Joint swelling
  • Gastrointestinal distress
  • Unexplained weight loss
  • Night sweats
Duration of symptoms Several hours up to two weeks  Months to years
  • NSAID medications (such as ibuprofen and naproxen)
  • Ice
  • Rest
  • Exercise
  • NSAIDs
  • Steroids
  • Immunosuppressants or immune modulators
  • Biologic treatments
  • Lifestyle changes

Prevalence of inflammatory disease

Almost 50% of Americans live with a chronic illness, according to the Centers for Disease Control and Prevention. Seven of the 10 leading causes of death in the United States can be attributed to chronic diseases like heart disease, stroke, diabetes, cancer, obesity, and arthritis. These diseases often cause systemic inflammation.

“Almost all of the most common diseases—from obesity to Crohn’s disease, are considered to be inflammatory diseases,” Dr. Davidson says. Inflammatory disease is any disease in which there is recruitment of white blood cells to the site of injury. Chronic inflammation can lead to thickened walls of the blood vessels, resulting in organ and tissue damage.

What causes inflammation?

The main cause of inflammation in the body is injury or irritation, which prompts your body to send inflammatory cells to the spot to help heal it, says Kathryn A. Boling, MD, primary care provider at Mercy Personal Physicians in Lutherville, Maryland. But sometimes, an autoimmune issue occurs. That’s when “your body identifies something inside of you, decides it doesn’t belong there, and starts attacking it again and again,” she says. This type of immune response can cause tissue damage and even lead to chronic disease.

When it comes to differentiating between acute and chronic inflammation, time is the primary factor to consider. “Acute means recent and short-lived,” Dr. Davidson says. “Chronic means ongoing and long-lasting.”

Causes of acute inflammation

  • Injuries such as sprains, strains, scrapes, and breaks
  • Bacterial illnesses such as staphylococcus aureus and streptococcus
  • Viral illnesses such as the common cold, the flu, and gastroenteritis
  • Other pathogens including as yeast and fungal infections
  • Allergens such as pollen, poison ivy or poison oak, medications

Causes of chronic inflammation

  • Diabetes
  • Obesity
  • Heart disease
  • Respiratory disease
  • Cancer
  • Rheumatoid arthritis
  • Gout
  • Lupus
  • Crohn’s disease
  • Ulcerative colitis
  • Hashimoto’s thyroiditis
  • Hepatitis C
  • Alzheimer’s disease
  • Exposure to environmental irritants/allergens or chemical toxins

Two major risk factors for inflammatory disease are smoking and obesity. Chronic stress and alcohol use are also linked to inflammation. “There are also genetic risks that are disease specific, making some diseases hereditary,” Dr. Davidson says. “Additionally, environmental risks like exposure to dust and fumes could lead to inflammatory disease.”

RELATED: What is post-viral fatigue syndrome?

Inflammation symptoms

Pain is a side effect of both acute and chronic inflammation. “If you have Crohn’s disease and you have inflammation in your GI tract, you’ll have pain,” Dr. Boling says. “If you strain your back because you just did a deadlift with way too much weight, you’ll have pain.” Pain is typically the first symptom you’ll feel from inflammation. It’s also normal to experience tissue changes that cause swelling or redness. “That can happen even when an autoimmune disease is causing the inflammation,” Dr. Boling adds. “I’ve had patients come in with a spot on their throat that is really tender and sore to touch, and it turns out to be Hashimoto’s thyroiditis.”

When your body is overcome by inflammation, it sends off different healing factors—fluids, and blood cells—and that causes swelling. When the body produces an inflammatory response for a long time, those cells release a large amount of chemicals that are destructive to normal tissue, causing pain and the breakdown of normal bodily functions. “There’s only so much room in the different compartments of our body to hold all of that fluid, so the site of infection starts to push on our nerve endings, and our nerve endings hold our pain factors,” Dr. Ascher explains. “That’s why we feel pain with inflammation.”

Classic symptoms of acute inflammation include:

  • Pain
  • Swelling
  • Warmth and redness to the area
  • Loss of function
  • Joint pain and stiffness 
  • Fever

Other symptoms can occur, too. When the body sends out inflammatory cells, “oftentimes there’ll be fatigue, we’ll have flu-like symptoms, and we’ll be a little feverish. It’s the body’s way of overcoming whatever reaction it’s trying to fight,” says Dr. Ascher.

In addition to the above symptoms, chronic inflammation can cause:

  • Persistent fatigue
  • Achiness
  • General feelings of unwellness
  • Unexplained weight loss
  • Bloating
  • Fever
  • Night sweats
  • Diminished mental function


While there is no one test that can diagnose inflammation, your provider will assess your symptoms, conduct a physical exam, and may order appropriate testing—including blood tests to identify inflammatory markers such as C-reactive protein (CRP) in the blood. 

“Any time a patient comes in to see me and mentions that they have weight loss, joint pain, fatigue, fevers, or night sweats, I always do a laboratory work-up, sometimes with imaging [tests], to clue me into what inflammatory disease process we’re looking at,” Dr. Ascher says. 

Each inflammatory disease has its own set of symptoms and physical findings. Based on these, your physician will order different diagnostic tests to help make the final diagnosis. Many of the lab tests for inflammation are non-specific, so it may take time and patience to determine the specific cause or process. 

Inflammation treatment

If you suffer from an injury, it’s best to ice the spot right away to fight inflammation. “Take a nonsteroidal anti-inflammatory, [like ibuprofen Motrin or naproxen Aleve] (as long as you’re not taking a blood thinner or other contraindicated medication) to decrease inflammation,” Dr. Boling says. Then, be careful not to reinjure the same area. 

For chronic inflammation, your healthcare provider might prescribe a daily NSAID, steroid, immunosuppressant, or biologic medication. “If you have chronic inflammation, the most important thing is to follow an anti-inflammatory diet, [consuming] things like vegetables, fruit, and any non-processed foods (avoid heavily processed foods that have multiple ingredients with multiple different chemical components),” says Dr Ascher. Fried foods and carbohydrates that contain a lot of added sugar should also be limited. Replace trans fat with healthier options, such as olive oil.

Lowering your risk factors through lifestyle changes is a powerful way to reduce inflammation. Limiting sugar and alcohol intake, avoiding smoking, staying physically active, having a good sleep schedule, and maintaining a healthy weight will increase your overall wellness and decrease inflammation. Mindfulness and meditation can also reduce your stress level, which is important when dealing with inflammation.

“Ultimately, the best way to treat inflammation is by treating the underlying disease and by avoiding risk factors,” Dr. Davidson says. Sometimes surgery is necessary to treat the underlying cause of the inflammation, such as inflammatory bowel disease

“Another exciting area being investigated by the Feinstein Institutes for Medical Research is bioelectronic medicine, or the ability to electrically stimulate the body’s nerves either with an implanted device or non-invasively to help turn off the body’s inflammation,” Dr. Davidson says. “There are clinical trials looking at vagus nerve stimulation for rheumatoid arthritis and other inflammatory and autoimmune disorders. These are so far investigational and efficacy will need to be proven in placebo controlled studies before this approach becomes available for patients to use.”

Common treatments for inflammation include: 

RELATED: Anti-inflammatory benefits of turmeric


To reduce inflammation in the body, it’s important to lower the risk factors that are within your control. If you drink alcohol, limit yourself to one drink a day, and if you’re a smoker, quit. “Stay on a healthy diet and try to maintain a healthy weight; lots of sugary and processed foods [as well as red or processed meat] are going to cause inflammation in your body,” says Dr. Boling. “You just have to be really careful about what you’re eating and what you’re putting into yourself.” Also, a good sleep schedule is important to your wellbeing. 

Following a regular exercise routine and adhering to your healthcare provider’s recommended healthcare regimen can have a huge impact on inflammation. If you’re experiencing signs of inflammation, consult with your physician for medical advice.