Lupus develops when your immune system attacks your own tissues, but doctors do not yet know exactly why this happens in some people and not others

Lupus is an autoimmune disease, meaning your body's immune system mistakenly treats your own cells as invaders and attacks them. This causes inflammation in joints, skin, kidneys, heart, lungs, and blood vessels. The disease is not contagious and you cannot catch it from another person. What remains unclear is why your immune system turns against you in the first place.

No single cause has been identified. Instead, lupus appears to result from a combination of factors: your genes, your hormones, and something in your environment that triggers the disease in a person who is genetically vulnerable. This is why lupus runs in families but does not always develop in everyone who carries the genetic risk.

Key Takeaways

  • Lupus occurs when your immune system attacks your own tissues, but the exact trigger remains unknown.
  • Genetics play a role—lupus runs in families—but having the genes does not may provide you will develop the disease.
  • Hormones, particularly estrogen, influence lupus risk, which is why the disease is far more common in women.
  • Environmental factors such as sun exposure, infections, and certain medications may trigger lupus in people who are genetically predisposed.
  • Lupus is not caused by anything you did, and you cannot catch it from or give it to another person.

The role of genetics in lupus development

If a parent or sibling has lupus, your risk of developing it is higher than the general population. Studies of identical twins show that when one twin has lupus, the other develops it only about 25 percent of the time—meaning genetics loads the gun, but something else pulls the trigger.

Researchers have identified multiple genes associated with lupus, including genes that control how your immune system responds to infection and how it clears dead cells from your body. People of African, Hispanic, Asian, and Native American descent have higher rates of lupus than people of European descent, suggesting genetic variation across populations.

Having these genes does not mean you will develop lupus. Many people carry lupus-related genes and never become ill. This is why doctors focus on both family history and other risk factors when assessing your likelihood of developing the disease.

How hormones affect lupus risk

Lupus is diagnosed in women nine times more often than in men, and this difference is largely driven by estrogen. Women in their reproductive years—when estrogen levels are highest—face the greatest risk. Lupus often first appears in women between ages 15 and 45.

Estrogen appears to strengthen immune responses in ways that increase the risk of autoimmune attack. Men with lupus sometimes have lower testosterone levels, and testosterone may actually protect against autoimmune disease. Pregnancy can trigger or worsen lupus in some women, and some women find their symptoms improve after menopause when estrogen levels drop.

Hormonal birth control and hormone replacement therapy may increase lupus risk in women who are genetically vulnerable, though the effect is modest. If you have a family history of lupus and are considering these medications, discuss the risk with your doctor.

Environmental triggers that may activate lupus

Ultraviolet (UV) light from the sun is the most well-documented environmental trigger. Sun exposure can cause lupus skin rashes and may trigger or worsen systemic lupus in some people. This does not mean lupus is caused by sun exposure alone, but rather that sun exposure may activate the disease in someone already at risk.

Infections—particularly viral infections such as Epstein-Barr virus—have been linked to lupus development. Some people develop lupus symptoms shortly after a serious infection. Certain medications, including some antibiotics and blood pressure drugs, can trigger a lupus-like syndrome, though this usually resolves when the medication is stopped.

Smoking, stress, and physical trauma have also been reported as potential triggers in some cases, though the evidence is less clear than it is for UV light and infection. No single environmental factor causes lupus on its own; rather, these factors may activate the disease in genetically predisposed individuals.

Why some people develop lupus and others do not

The most accurate way to think about lupus is as a disease of genetic susceptibility plus environmental trigger. You might inherit genes that make autoimmune disease more likely, but you also need something to activate those genes—an infection, sun exposure, hormonal change, or something else not yet identified.

This explains why lupus clusters in families but does not affect everyone in the family. It also explains why identical twins do not always both develop the disease. Two people with identical genes may have very different environmental exposures, stress levels, or infection histories.

Researchers continue to study what specific combinations of genes and environmental factors lead to lupus. Understanding these mechanisms may eventually lead to ways to prevent the disease in high-risk people, but that research is still ongoing.

What lupus is not caused by

Lupus is not caused by anything you did. You cannot develop lupus from poor diet, lack of exercise, stress alone, or any personal choice. It is not contagious—you cannot catch it from someone else, and you cannot give it to another person through contact, blood, or any other means.

Lupus is not caused by a weak immune system. In fact, the opposite is true: lupus results from an immune system that is overactive and misdirected. It is also not caused by a single infection, though infection may trigger it in someone genetically vulnerable.

Frequently Asked Questions

If my mother has lupus, will I definitely develop it?

No. Having a parent with lupus increases your risk, but most children of people with lupus do not develop the disease. Your risk depends on which genes you inherited and what environmental exposures you have. Discuss your family history with your doctor if you develop symptoms.

Can lupus be prevented if it runs in my family?

There is no proven way to prevent lupus in someone at genetic risk. However, minimizing sun exposure, managing stress, avoiding smoking, and treating infections promptly may reduce the chance of triggering the disease in a genetically vulnerable person. Talk with your doctor about your specific risk factors.

Does lupus skip generations?

Lupus can appear to skip generations because having the genes does not may provide you will develop the disease. A parent may carry lupus genes without ever becoming ill, then pass those genes to a child who does develop lupus when exposed to the right environmental trigger.

Can men get lupus?

Yes, though it is less common. Men account for about 10 percent of lupus cases. Men with lupus often have more severe kidney involvement than women, and they may develop the disease later in life. The reasons for these differences are not fully understood.

Is lupus caused by the sun?

Sun exposure can trigger or worsen lupus in people who already have the disease, but it does not cause lupus on its own. You need genetic predisposition plus a trigger—sun exposure is one possible trigger, but not the only one and not necessary for everyone.