Immunotherapy can be painful for some patients, but pain is not universal, and the experience varies significantly depending on the type of immunotherapy used and how an individual’s body responds. The most common sources of pain include joint and muscle aches, skin reactions such as rash or irritation, discomfort at the infusion or injection site, and inflammation-related pain affecting organs like the lungs, colon, or other tissues. While many patients experience only mild discomfort or no significant pain at all, some develop serious immune-related inflammation that requires prompt medical evaluation and active management. 

What Types of Pain Does Immunotherapy Cause?

Some of the most common types of pain associated with immunotherapy include joint and muscle pain, skin irritation, mouth sores, and flu-like body aches. These symptoms occur because immunotherapy stimulates the immune system, which can sometimes lead to inflammation in healthy tissues as well as cancer cells. The severity of pain varies widely, ranging from mild discomfort to symptoms that significantly affect daily activities.

• Joint and Muscle Pain (Arthralgia and Myalgia)
  Joint and muscle pain are among the most frequently reported side effects of immunotherapy. In some patients, the activated immune system mistakenly attacks healthy joint or muscle tissue, causing inflammation. Symptoms may range from mild stiffness and soreness to significant pain, swelling, and reduced mobility that can interfere with normal activities.
• Skin Pain and Irritation
  Immunotherapy can cause a variety of skin-related side effects, including rashes, redness, itching, dryness, and blistering. Certain immunotherapy and targeted immunotherapy treatments are more likely to trigger skin reactions. While some cases are mild, more severe skin inflammation can lead to significant discomfort, tenderness, and sensitivity.
• Mouth Sores
  Some patients develop painful sores, ulcers, or inflammation inside the mouth during treatment. These mouth sores can make eating, drinking, and speaking uncomfortable. Symptoms may range from mild tenderness to more severe ulceration that requires supportive care and medical management.
• Headaches and Generalized Body Aches
  Flu-like symptoms are common after some immunotherapy infusions. Patients may experience headaches, fatigue, chills, and widespread body aches, particularly during the first few days following treatment. These symptoms are often temporary but can be uncomfortable and may recur with subsequent treatment cycles.

Infusion Site Reactions

For patients receiving immunotherapy through an intravenous (IV) infusion, the infusion site itself can sometimes be a source of discomfort. Common symptoms include redness, swelling, bruising, or tenderness around the needle insertion site. Some patients also experience a mild burning, stinging, or aching sensation during the infusion or shortly afterward.

In rare cases, a complication known as thoát mạch may occur, where the medication leaks from the vein into the surrounding tissue. This can cause more significant localized pain, swelling, and irritation and may require prompt medical evaluation and treatment to prevent tissue damage.

In addition to local infusion-site discomfort, some patients experience infusion reactions while the medication is being administered. These reactions can cause symptoms such as chills, flushing, fever, chest tightness, shortness of breath, dizziness, or itching. Infusion reactions are generally more common during the first few treatment sessions and are often closely monitored by the healthcare team. Most reactions can be managed by slowing or temporarily stopping the infusion and providing supportive medications when necessary.

Inflammation-Driven Pain — When the Immune System Overreacts

The most serious pain associated with immunotherapy often comes from immune-related adverse events (irAEs). These occur when the immune system becomes overactive and mistakenly attacks healthy organs or tissues. Unlike mild body aches or temporary infusion-related discomfort, irAEs can cause deeper, persistent, or worsening pain that may signal inflammation in a specific organ.

Key organ-specific pain presentations are:

• Viêm phổi, or inflammation of the lungs, can cause chest pain, chest tightness, shortness of breath, and a persistent cough. These symptoms should be reported promptly, especially if they worsen or occur with difficulty breathing.
• Colitis, or inflammation of the intestines, may cause abdominal cramping, stomach pain, and diarrhea. In some cases, diarrhea can become frequent or severe and may be accompanied by blood, dehydration, or significant abdominal tenderness.
• Viêm gan, or inflammation of the liver, is less likely to cause sharp or obvious pain, but it may lead to fatigue, nausea, abnormal liver tests, or discomfort in the right upper area of the abdomen.
• Inflammatory arthritis can cause more persistent joint swelling, stiffness, warmth, and pain. This is different from milder muscle aches or temporary soreness because it may limit movement and continue between treatment cycles.

Any new, worsening, or persistent pain during immunotherapy should be reported to the healthcare team as soon as possible. Early recognition and treatment of immune-related adverse events can help prevent complications, reduce symptom severity, and improve outcomes.

Is Immunotherapy More or Less Painful Than Chemotherapy?

Immunotherapy and chemotherapy can both cause discomfort, but they produce pain in different ways. Chemotherapy is commonly associated with tác dụng phụ such as nausea, painful mouth sores (mucositis), peripheral neuropathy (nerve pain in the hands and feet), fatigue, and the bone pain that can occur with treatment-related low blood cell counts. Immunotherapy, by contrast, is less likely to cause neuropathy, severe mucositis, or chemotherapy-related bone pain.

However, immunotherapy has its own unique pain profile. Because these treatments activate the immune system, they can trigger inflammation in healthy tissues, leading to joint pain, muscle aches, abdominal pain from colitis, chest discomfort from lung inflammation, and other immune-related adverse events. These inflammation-driven symptoms are generally less common with traditional chemotherapy and can sometimes become serious if not recognized and treated promptly.

For many patients, immunotherapy is perceived as easier to tolerate than chemotherapy because it often causes fewer day-to-day side effects. However, that does not necessarily mean it is less painful. The nature of the pain is simply different. While one patient may experience only mild fatigue and occasional joint aches, another may develop significant immune-related inflammation that requires medical intervention.

Ultimately, the overall pain burden of immunotherapy versus chemotherapy varies considerably from person to person. Factors such as the specific drugs used, the type of cancer being treated, a patient’s underlying health, and individual immune response all influence how treatment is experienced. Rather than being universally more or less painful, immunotherapy and chemotherapy are best understood as having distinct side-effect and pain profiles.

How Is Immunotherapy-Related Pain Managed?

The treatment approach for immunotherapy-related pain depends on its severity, underlying cause, and whether it is associated with an immune-related adverse event (irAE). Early recognition and appropriate management are important for maintaining quality of life and preventing complications.

Vì mild pain, healthcare providers may recommend over-the-counter pain relievers such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs), when appropriate. Skin-related discomfort may be managed with topical creams, moisturizers, or prescription treatments, while antihistamines can help relieve itching associated with rashes and other skin reactions.

Đau khớp và cơ are among the more common side effects of immunotherapy and may benefit from a combination of physical therapy, stretching exercises, anti-inflammatory medications, and other supportive measures. In some cases, treatment schedules may be adjusted or temporarily modified if symptoms begin to interfere with daily activities.

When pain is caused by a serious immune-related adverse event, more aggressive treatment may be necessary. Corticosteroids such as prednisone or methylprednisolone are the primary therapies used to reduce immune-driven inflammation affecting the joints, lungs, intestines, liver, or other organs. Depending on the severity of the reaction, immunotherapy may be temporarily paused or, in some cases, permanently discontinued to protect patient safety.

Patients can play an important role in managing treatment-related pain by keeping a symptom log and tracking when symptoms occur, how severe they are, and whether they are improving or worsening. Sharing this information with the care team at every visit can help clinicians identify potential complications early and make timely adjustments to treatment and symptom-management strategies.