Liver inflammation, known as hepatitis, is the body’s immune response to liver damage or infection. An inflamed liver struggles to perform functions like clearing toxins, producing bile, and regulating fat storage.
Liver inflammation can be acute, appearing suddenly and resolving quickly, or chronic, persisting over six months. Acute inflammation aims to clear infections and heal, but if the cause persists, chronic inflammation can develop. Chronic inflammation can lead to scar tissue (fibrosis) and severe conditions like cirrhosis or liver failure.
Viral Infections
Viral hepatitis is a common cause of liver inflammation, caused by specific viruses. Hepatitis A, B, and C are the most prevalent types, each with distinct transmission routes and outcomes.
Hepatitis A (HAV) is primarily transmitted through the fecal-oral route, spreading when an uninfected person ingests food or water contaminated with an infected person’s stool, often through close contact or contaminated food/drink. It causes an acute infection that usually resolves without treatment, leading to immunity.
Hepatitis B (HBV) is transmitted through contact with infected blood or other body fluids, including sexual fluids. Transmission occurs through unprotected sex, sharing needles, or from mother to baby during childbirth. Many adults clear acute HBV, but it can become chronic, especially if acquired in infancy or early childhood. Chronic HBV can lead to liver damage, including cirrhosis and liver cancer.
Hepatitis C (HCV) is spread primarily through blood-to-blood contact, like sharing needles, or less commonly, through sexual contact or from mother to baby. Like HBV, HCV can cause chronic infection, leading to serious liver damage if untreated. Unlike HAV and HBV, there is no vaccine for HCV. Less common forms include Hepatitis D, which only affects those with HBV, and Hepatitis E, an acute infection transmitted through contaminated water.
Lifestyle and Metabolic Factors
Lifestyle choices and metabolic conditions significantly contribute to liver inflammation. Two prominent examples are alcoholic liver disease and non-alcoholic fatty liver disease (NAFLD). These conditions highlight how daily habits and underlying health issues can impact liver health.
Alcoholic liver disease (ALD) results from excessive alcohol consumption, which generates toxic metabolites like acetaldehyde and reactive oxygen species during its breakdown in the liver. These substances directly damage liver cells and trigger inflammatory responses. Alcohol also increases the permeability of the gut, allowing bacterial products to enter the bloodstream and activate inflammatory pathways in the liver. Chronic alcohol use sensitizes liver cells to inflammatory signals, impairing their ability to respond to protective mechanisms.
Non-alcoholic fatty liver disease (NAFLD) is characterized by fat accumulation in the liver, occurring in individuals who consume little to no alcohol. This condition is strongly linked to metabolic factors such as obesity, type 2 diabetes, insulin resistance, and high levels of fats in the blood. When fat accumulation in the liver is accompanied by inflammation and liver cell damage, the condition progresses to non-alcoholic steatohepatitis (NASH). NASH is a more severe form of NAFLD that can lead to fibrosis, cirrhosis, and liver cancer. The global increase in obesity and type 2 diabetes has made NAFLD and NASH increasingly common causes of liver inflammation.
Immune System and Medication Reactions
The immune system, while protective, can sometimes mistakenly attack the liver, leading to inflammation. Additionally, certain medications can induce liver injury as an adverse effect. These distinct pathways illustrate how internal immune responses and external chemical exposures can harm the liver.
Autoimmune hepatitis occurs when the body’s immune system incorrectly identifies its own liver cells as foreign invaders and mounts an attack against them. This leads to chronic inflammation and can cause progressive liver damage. The exact cause of autoimmune hepatitis is not fully understood, but it is believed to involve a combination of genetic predispositions and environmental triggers, such as certain infections or medications. The immune system produces autoantibodies that target liver cells, leading to their destruction.
Drug-induced liver injury (DILI) refers to liver inflammation caused by certain medications, supplements, or herbal remedies. The liver is responsible for metabolizing many substances, making it susceptible to damage from toxic byproducts. Common culprits include acetaminophen, especially in overdose, and certain antibiotics like amoxicillin-clavulanate. Other medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), some anti-epileptic drugs, and statins can also cause DILI. The severity of DILI can vary, ranging from mild enzyme elevations to acute liver failure, highlighting the importance of consulting a healthcare provider about any new medication or supplement use.
Genetic and Other Less Common Factors
Beyond viral infections, lifestyle, and immune system issues, several less common or genetic factors can also contribute to liver inflammation. These conditions often involve the accumulation of substances that become toxic to the liver.
Genetic conditions can disrupt the body’s normal metabolic processes, leading to the buildup of harmful substances in the liver. Hemochromatosis, for example, is an inherited disorder characterized by excessive iron absorption and accumulation in the liver and other organs. This iron overload can cause inflammation and damage to liver cells. Wilson’s disease is another genetic disorder where the body cannot properly excrete copper, leading to its toxic accumulation in the liver, brain, and other tissues. The excess copper causes inflammation and can result in severe liver damage.
Alpha-1 antitrypsin deficiency (AATD) is a genetic condition where the liver produces an abnormal alpha-1 antitrypsin protein that cannot be properly released from liver cells. This misfolded protein accumulates within the liver, causing stress, inflammation, and cellular damage. While many individuals with AATD may not develop severe liver disease, some can experience chronic hepatitis, cirrhosis, or even liver cancer. Other less common causes of liver inflammation include rare infections, such as parasitic infections, and exposure to certain environmental toxins like industrial chemicals or poisonous mushrooms. Heavy metals, pesticides, and certain volatile organic compounds can also lead to liver damage and inflammation.