The medical term for an inflamed liver is hepatitis, which means inflammation of the liver tissue. The liver is the largest internal organ, performing over 500 functions fundamental to survival, including filtering blood, detoxifying chemicals, and metabolizing nutrients. When the liver becomes inflamed, its specialized cells are damaged, which impairs its ability to convert food into energy, eliminate waste, and regulate fat storage. Persistent inflammation triggers the body’s repair system, which can lead to scarring (fibrosis), a process that eventually compromises the liver’s overall function.
Viral and Infectious Agents
The most common causes of liver inflammation worldwide are viral infections: Hepatitis A, B, and C viruses. These agents directly infect the liver tissue but differ significantly in their transmission and long-term effects. Hepatitis A virus (HAV) is typically spread through the fecal-oral route, often by consuming contaminated food or water.
Infection with HAV usually causes an acute, short-term illness that the body clears on its own, generally without leading to chronic liver injury. In contrast, Hepatitis B virus (HBV) and Hepatitis C virus (HCV) are primarily transmitted through contact with infected blood and other bodily fluids, such as via unprotected sex, shared needles, or from mother to child at birth.
Both HBV and HCV can establish chronic infections that persist for years, causing ongoing inflammation. This long-term injury drives the progression of liver damage, leading to extensive scarring (cirrhosis) over time. Hepatitis C, in particular, has historically been the leading reason for liver transplants in the United States due to its tendency to cause chronic disease.
Lifestyle-Related Factors
Chronic exposure to certain lifestyle factors is a highly prevalent cause of liver inflammation. These causes fall into two categories: those related to metabolic health and those linked to substance use. Non-Alcoholic Fatty Liver Disease (NAFLD) is tied to metabolic issues like obesity and insulin resistance, causing an excessive accumulation of triglycerides within the liver cells.
When the fat accumulation, known as steatosis, progresses, it triggers an inflammatory response. This stage is called Non-Alcoholic Steatohepatitis (NASH), where inflammation and hepatocyte injury accelerate the development of fibrosis and cirrhosis. The liver’s attempt to manage the constant influx of free fatty acids leads to oxidative stress, which drives the inflammatory signaling.
The second major lifestyle cause is Alcohol-Related Liver Disease (ALD), which occurs following chronic, excessive consumption of alcohol. Alcohol is metabolized in the liver, and the toxic byproducts directly damage the liver cells and activate inflammatory pathways. ALD can manifest as simple fatty liver (steatosis), acute alcoholic hepatitis (inflammation), or advanced scarring (cirrhosis), with severity depending on the duration and quantity of alcohol consumed.
Drug Toxicity and Environmental Exposure
The liver’s role as the body’s main detoxifying organ makes it susceptible to injury from various chemical compounds, a condition known as Drug-Induced Liver Injury (DILI). Medications, whether prescribed or over-the-counter, must be broken down by the liver, a process that sometimes creates reactive metabolites that can damage hepatocytes. This injury can be intrinsic (predictable and dose-dependent) or idiosyncratic (less predictable and potentially involving an immune reaction).
A common example of intrinsic liver injury is an overdose of acetaminophen, a widely used pain reliever, which is the most frequent cause of acute liver failure in the United States. Beyond pharmaceuticals, certain herbal and dietary supplements (HDS) are recognized as a cause of DILI, as their ingredients and concentrations are not always consistent or regulated. Environmental exposure also contributes, such as ingesting toxins like poisonous mushrooms or chronic exposure to industrial chemicals, which can cause acute inflammation.
Autoimmune and Genetic Conditions
Liver inflammation can result from a malfunction of the body’s internal systems, rather than an external attack or lifestyle choice. Autoimmune Hepatitis (AIH) occurs when the immune system mistakenly identifies liver cells as foreign and launches an attack against them. This causes chronic inflammation that, if untreated, can lead to progressive scarring and liver failure.
Genetic disorders can also predispose an individual to liver inflammation by causing a toxic buildup of substances the liver normally manages. Hemochromatosis is an inherited condition that causes the body to absorb excessive amounts of iron from the diet, leading to iron overload in the liver tissue. This accumulation generates oxidative stress that triggers chronic inflammation and fibrosis. Similarly, Wilson’s Disease is a rare inherited disorder where the body cannot properly eliminate copper, causing the metal to accumulate in the liver and brain, resulting in chronic liver damage.