Immunotherapy and Swelling: What to Expect and How to Cope

Immunotherapy can cause swelling in different parts of the body because it activates the immune system, which may inflame normal tissues as well as cancer. This can show up as skin and joint swelling, limb swelling, or internal inflammation such as colitis (swelling of the large intestine). ^[1] These immune-related side effects are usually manageable, especially when recognized and treated early. ^[1]

Why swelling happens

• When the immune system is stimulated by treatments like PD-1, PD-L1, or CTLA-4 inhibitors, it can occasionally overreact and inflame healthy tissues, leading to symptoms such as joint pain and swelling, limb swelling, skin issues, or organ inflammation. ^[1]
• For example, inflammation in the colon (immune-related colitis) can cause diarrhea and abdominal discomfort; this is a form of internal “swelling.” ^[2]

Common types of swelling with immunotherapy

• Joint inflammation: People may notice new or worsening joint pain, stiffness, and visible swelling around joints or limbs. ^[3]
• Limb swelling: Hands or feet can swell, sometimes alongside other symptoms (for example, with lung inflammation). ^[4]
• Gastrointestinal swelling: Inflammation in the colon can cause frequent, watery stools and cramping. ^[2]
• Skin and soft tissue: Rashes and irritation can be part of the broader inflammatory response. ^[1]

Red flags that need prompt medical contact

• New or rapidly worsening swelling of joints or limbs, especially if it limits movement or daily activities. ^[3]
• Diarrhea more than three watery stools per day, blood in stool, severe cramping, or a sudden change in bowel habits, which can signal colitis. ^{[2] [5]}
• Swelling associated with shortness of breath, chest pain, new or worse cough, or general decline, which can signal lung involvement and needs urgent evaluation. ^[4]

How to cope safely at home (when mild)

• Rest and protect swollen joints; use gentle range-of-motion exercises to avoid stiffness if your team says it’s okay. ^[3]
• Apply cool compresses to mildly swollen joints or limbs to reduce discomfort, and elevate the limb when possible. ^[3]
• For skin irritation, wear loose clothing, protect from sun exposure, and use gentle skin care (fragrance-free moisturizers, sunscreen SPF 30+). ^[6]
• Stay well hydrated and eat bland foods if you have mild gut symptoms; however, do not self-treat diarrhea without guidance. ^[5]

What treatments your care team may use

• Your clinicians may recommend topical treatments (such as steroid creams for rash) and analgesics for mild joint symptoms. ^[6]
• If symptoms suggest immune-related inflammation (moderate to severe), your team may pause immunotherapy and start anti-inflammatory medicines such as corticosteroids to calm the immune response, with close monitoring and a careful taper. ^[7]
• Management follows graded severity; early reporting allows faster relief and reduces the risk of escalation. ^{[8] [7]}

Practical do’s and don’ts

• Do report new or worsening swelling, pain, diarrhea, or breathing changes right away; early action prevents complications. ^{[1] [2]}
• Do not start over-the-counter anti-diarrheal medications without approval, because treatment differs if swelling is immune-related colitis. ^[5]
• Do follow sun protection, gentle skin care, and comfortable clothing to reduce skin irritation related to immune activation. ^[6]

When to call urgently

• More than three watery stools per day, blood in stool, or severe abdominal pain. ^{[2] [5]}
• Swelling with shortness of breath, chest pain, or a rapidly worsening cough. ^[4]
• Marked joint or limb swelling that suddenly worsens or prevents normal activity. ^[3]

Bottom line

Swelling can happen during immunotherapy as part of immune-related side effects, including joint or limb swelling, skin irritation, and internal inflammation such as colitis. Early recognition and prompt communication with your care team make these effects much more manageable and help keep treatment on track. ^{[1] [3] [2] [5] [6] [7]}