Can Immunotherapy Cause Headaches, and How Can You Cope?

Yes, headaches can occur with cancer immunotherapy, and they range from mild to rarely serious. Common immune therapies (like checkpoint inhibitors) can trigger flu-like symptoms that include headache, and they may also affect hormone glands (thyroid, pituitary, adrenal), which can lead to persistent headaches. ^[1] Headaches are also noted in patient guidance for multiple immunotherapy regimens. ^{[2] [3] [4]}

While most headaches are mild and manageable, urgent symptoms such as severe headache with fever, neck stiffness, confusion, extreme light sensitivity, or new neurologic changes may signal rare but serious inflammation of the brain or its lining (encephalitis or meningitis) and require immediate medical care. ^{[5] [6] [7]}

---

Why Headaches Happen with Immunotherapy

• Flu-like reaction to treatment: Headache may occur with general symptoms like fever, chills, and fatigue. ^[1]
• Hormone (endocrine) side effects: Immune-related thyroiditis, hypophysitis (pituitary), or adrenal issues can cause headaches that don’t go away, often alongside fatigue, dizziness, weight change, or feeling cold. ^[8]
• Rare neurologic inflammation: Meningitis or encephalitis can present with headache, fever, confusion, muscle weakness, neck stiffness, and marked sensitivity to light. ^{[5] [6] [7]}

---

When to Seek Medical Care

• Immediately (Emergency): Severe or rapidly worsening headache, headache with fever, neck stiffness, confusion, vision changes, severe light sensitivity, fainting, or muscle weakness. These could indicate meningitis/encephalitis and need urgent evaluation. ^{[5] [6] [7]}
• Promptly (Call your oncology team): Headaches that won’t go away or are not relieved by usual pain medicines, especially if accompanied by extreme tiredness, dizziness, weight changes, or feeling unusually cold (possible hormone gland problems). ^[8]
• Soon (within a day or two): New or changing headache patterns, headaches that persist for several days, headaches worse in the morning, or if your immune system is weakened by cancer treatment. ^[9]

---

Practical Ways to Cope at Home

• Use simple pain relief first-line: Paracetamol (acetaminophen) is commonly recommended for headache unless your care team has advised otherwise. ^{[10] [11] [12] [13] [14]}
• Hydration and rest: Keeping well hydrated and resting can ease flu-like headache symptoms. ^[1]
• Gentle daily activity: Light exercise may help reduce tension and improve overall well-being, which can lessen headache frequency. ^{[11] [12] [13] [14]}
• Light and screen management: If you are light-sensitive, reduce screen glare, use dim lighting, and consider sunglasses outdoors; report extreme light sensitivity, as it can be a warning sign if severe. ^{[5] [6] [7]}
• Monitor for patterns: Track timing, triggers, severity, and associated symptoms (fever, vision changes, dizziness) to share with your oncology team for better tailoring of care. ^[9]

---

Treatments Your Care Team May Consider

• Evaluation for endocrine causes: If headaches persist or you have red flags like fatigue, dizziness, weight change, or feeling cold, your team may check thyroid, pituitary, and adrenal function and treat any hormone issues found. ^[8]
• Assessment for neurologic irAEs: For severe or atypical headaches, clinicians may evaluate for meningitis or encephalitis and treat promptly, often with steroids if an immune-related inflammation is suspected. ^{[5] [6] [7]}
• Pain management plan: Your team might adjust your regimen and provide specific pain strategies; they also advise you to take any prescribed steroids or pain relievers exactly as directed. ^{[2] [3] [4]}

---

Red-Flag Symptoms at a Glance

• Severe headache not helped by pain medicine. ^{[10] [11] [12] [13] [14]}
• Headache with fever, neck stiffness, confusion, memory problems, hallucinations, severe muscle weakness, or marked light sensitivity. ^{[5] [6] [7]}
• Headache that is persistent with extreme tiredness, dizziness/fainting, weight change, feeling cold, or other signs of hormone imbalance. ^[8]
• New or changing pattern of headaches, headaches that last more than a few days, or headaches worse in the morning. ^[9]

---

Quick Reference Table

Situation	What it may suggest	What to do
Mild headache with flu-like symptoms	Common treatment effect	Try paracetamol, rest, fluids; inform your team if it persists. [1] [10]
Persistent headache plus fatigue, dizziness, weight change, feeling cold	Possible endocrine side effect (thyroid/pituitary/adrenal)	Contact your oncology team for evaluation and labs. [8]
Severe headache with fever, neck stiffness, confusion, strong light sensitivity, or weakness	Possible meningitis/encephalitis (rare, serious)	Seek emergency care immediately. [5] [6] [7]
Very bad headache not relieved by pain meds	Needs urgent assessment	Call your team or go to the Emergency Department. [10] [11] [12] [13] [14]

---

Bottom Line

• Headache is a recognized side effect of immunotherapy, often mild but occasionally a sign of endocrine or neurologic inflammation. ^{[1] [8]}
• Use simple measures like paracetamol, rest, and hydration for mild cases, and contact your oncology team if headaches persist or change. ^{[10] [11] [12] [13] [14]}
• Get urgent help for severe headaches or any red-flag symptoms. ^{[5] [6] [7] [9]}