Lymphoma develops when white blood cells called lymphocytes acquire DNA damage that causes them to grow out of control. There is no single cause. Instead, a combination of factors can raise your risk, including certain infections, chemical exposures, a weakened immune system, family history, and body weight. Most people diagnosed with lymphoma have no obvious explanation for why it happened.
There are two main categories: Hodgkin lymphoma and non-Hodgkin lymphoma (NHL). NHL is far more common, with roughly 79,000 new cases expected in the United States in 2026 and a median age at diagnosis of 68. Hodgkin lymphoma tends to strike younger, often between ages 15 and 35 or after 55. The underlying process is similar in both types: something damages a lymphocyte’s DNA, the cell loses its ability to stop dividing, and it begins forming tumors in lymph nodes or other tissues.
What Goes Wrong Inside the Cell
Your immune system constantly produces lymphocytes, and those cells naturally rearrange their own DNA to build the receptors they need to fight infections. That rearrangement process is tightly controlled, but it creates a window of vulnerability. If a cell’s DNA repair machinery is faulty, the rearrangement can go wrong, causing pieces of chromosomes to swap places or genes that control growth to get permanently switched on. When the cell also lacks the ability to detect and destroy those errors (a function handled by a tumor-suppressor gene called p53), it can begin multiplying unchecked.
This is why lymphoma is fundamentally a disease of accumulated genetic errors rather than a single event. Some of those errors are inherited, some are triggered by infections, and some appear to arise from environmental exposures or simply from bad luck during normal immune cell production.
Viruses and Bacteria That Raise Risk
Several infections are directly linked to lymphoma through three distinct pathways.
Viruses that transform lymphocytes. Epstein-Barr virus (EBV), the virus behind mono, can infect B cells and insert proteins that hijack their growth controls. One protein in particular, called latent membrane protein-1, is considered the key driver of transformation. EBV is linked to Burkitt lymphoma, certain aggressive NHLs, and natural killer/T-cell lymphoma. Human T-lymphotropic virus type I (HTLV-1) and human herpesvirus 8 (HHV-8) work through a similar direct-infection mechanism.
Viruses that suppress immunity. HIV doesn’t transform lymphocytes directly. Instead, it destroys the immune cells that normally keep B lymphocytes in check, allowing those B cells to proliferate without regulation. People with AIDS have a markedly elevated risk of aggressive B-cell NHL.
Infections that cause chronic inflammation. The stomach bacterium H. pylori is the clearest example. When it colonizes the stomach lining, the body sends immune cells to fight it. That sustained immune response forces B cells to keep dividing, and the inflammatory chemicals released (including oxygen free radicals) can damage those cells’ DNA. Over time, a single B cell may acquire enough mutations to become cancerous. This is the origin of gastric MALT lymphoma, a slow-growing cancer that, when caught early, can sometimes be cured simply by treating the bacterial infection with antibiotics. Other chronic infections linked to localized MALT lymphomas include hepatitis C virus, Campylobacter jejuni in the small intestine, Chlamydia psittaci around the eye, and Borrelia afzelii in the skin.
Chemical and Environmental Exposures
Certain chemicals are associated with higher lymphoma rates, particularly among people with prolonged or heavy exposure. In 2015, the International Agency for Research on Cancer classified glyphosate, the active ingredient in the herbicide Roundup, as “probably carcinogenic to humans,” with the strongest evidence pointing to non-Hodgkin lymphoma. France’s national health research institute reached a similar conclusion in 2021. Studies of agricultural workers spraying glyphosate-based formulas with backpack sprayers show that nearly all of them (97.6% in one Thai study) had high levels of the chemical in their urine, with detectable amounts persisting into the next morning.
Benzene, certain other pesticides, and organic solvents have also been linked to lymphoma risk, though the evidence is strongest for occupational exposure over years rather than brief contact. For most people who aren’t regularly handling these chemicals, the added risk is small.
A Weakened Immune System
Anything that significantly weakens your immune system raises lymphoma risk, because your body becomes less able to detect and destroy abnormal lymphocytes before they multiply.
Organ transplant recipients face a specific threat called post-transplant lymphoproliferative disorder (PTLD). The immunosuppressive drugs they take to prevent organ rejection also suppress the T cells that normally patrol for cancerous B cells. PTLD can appear anywhere from a few months to several years after transplant. Risk is highest if the donor or recipient carries Epstein-Barr virus, because the suppressed immune system can no longer keep EBV in check.
Autoimmune conditions like rheumatoid arthritis, lupus, and celiac disease are also associated with higher lymphoma rates. The connection likely involves both the chronic immune stimulation from the disease itself and the immunosuppressive medications used to treat it.
Family History and Inherited Genes
An estimated 10% to 20% of blood cancers, including lymphomas, may involve an inherited genetic predisposition. Having a first-degree relative with any blood cancer significantly increases your own risk, even when no specific gene mutation has been identified in the family.
Several known inherited syndromes raise lymphoma risk. Li-Fraumeni syndrome, caused by mutations in the TP53 gene (the same tumor-suppressor gene involved in many lymphomas), is one of the most well-studied. Lynch syndrome, known for its link to colon cancer, also increases risk. Other conditions that impair DNA repair, including ataxia telangiectasia and Bloom syndrome, leave lymphocytes especially vulnerable to the kind of genetic errors that drive lymphoma. Mutations in the BRCA1, BRCA2, and CHEK2 genes, more commonly discussed in the context of breast cancer, are also associated with lymphoid cancers.
That said, most people with lymphoma have no identifiable hereditary syndrome. Family history raises risk but doesn’t determine outcomes.
Body Weight and Lifestyle Factors
Obesity is an increasingly recognized risk factor. A large Norwegian cohort study found that people with a BMI of 30 or higher had a 61% greater risk of Hodgkin lymphoma compared to those at a normal weight. Grade 2 obesity (BMI 35 and above) pushed that figure to 80% higher risk. The association was stronger in women, with each 5-point increase in BMI raising Hodgkin lymphoma risk by about 20%. Being obese in early adulthood (ages 16 to 29) carried an 89% increased risk, and obesity was also linked to earlier-onset disease, with diagnosis before age 50.
The biological explanation likely involves the chronic low-grade inflammation that accompanies excess body fat, along with changes in hormone levels and immune function. While the research on smoking and alcohol is less definitive for lymphoma than for other cancers, maintaining a healthy weight is one of the few modifiable factors with solid evidence behind it.
Why Most Cases Have No Clear Cause
Despite all these known risk factors, the majority of lymphoma cases cannot be traced to a single trigger. The disease results from a series of genetic accidents in lymphocytes, and most of those accidents happen during the normal, everyday work of the immune system. Age is the single biggest risk factor for non-Hodgkin lymphoma: the longer your immune cells have been dividing, the more opportunities for errors to accumulate. With nearly 873,000 people living with NHL in the United States as of 2023, it is one of the more common cancers, and most of those people had none of the risk factors listed above.
If you’re concerned about your own risk, the factors you can influence are limited but real: avoiding prolonged exposure to known chemicals, maintaining a healthy weight, and being aware of your family history so you can discuss screening with a doctor if needed.