Does immunotherapy cause hair loss? This is one of the most common questions asked by people starting cancer treatment in the UK. Unlike chemotherapy, which is well known for causing alopecia, immunotherapy works by stimulating the immune system rather than directly targeting rapidly dividing cells. As a result, significant hair loss is uncommon with most immunotherapy agents. However, immune-related adverse events — including alopecia areata and thyroid dysfunction — can occasionally affect hair, and understanding the distinction is essential for patients and carers navigating treatment.

Does Immunotherapy Cause Hair Loss?

Hair loss is uncommon with immunotherapy; checkpoint inhibitors rarely cause alopecia, though immune-related adverse events such as alopecia areata or thyroid-related hair thinning can occur in a small minority of patients.

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One of the most common concerns for people starting cancer treatment is whether they will lose their hair. Chemotherapy is well known for causing hair loss (alopecia), but immunotherapy works very differently — and its relationship with hair loss is considerably more nuanced.

Immunotherapy drugs, particularly checkpoint inhibitors such as pembrolizumab (Keytruda), nivolumab (Opdivo), and ipilimumab (Yervoy), work by stimulating the body's own immune system to recognise and attack cancer cells. Because they do not directly target rapidly dividing cells in the way chemotherapy does, hair loss is uncommon with most immunotherapy treatments. MHRA-approved Summary of Product Characteristics (SmPCs) for these agents classify alopecia as an uncommon or rare adverse effect, with frequencies typically below 1–2% depending on the agent and indication.

However, this does not mean hair changes are impossible. A small number of patients receiving checkpoint inhibitors have reported hair thinning, changes in hair texture, or, in rarer cases, a condition called alopecia areata — an autoimmune condition causing patchy hair loss. This occurs because immunotherapy can sometimes over-activate the immune system, leading it to mistakenly attack healthy tissues, including hair follicles. These are classified as immune-related adverse events (irAEs).

It is also important to be aware that thyroid dysfunction is a recognised irAE of checkpoint inhibitors. Hypothyroidism in particular can cause hair thinning and shedding, and may be mistaken for direct follicular damage. If you notice hair changes during immunotherapy, your clinical team may check thyroid function (TSH) and, where clinically indicated, other blood tests such as ferritin, to exclude reversible contributing causes.

Finally, it is important to distinguish between hair loss caused by immunotherapy and hair loss resulting from other aspects of cancer care. Many patients receive combination regimens that include chemotherapy alongside immunotherapy, and in these cases, chemotherapy is far more likely to be responsible for significant hair loss. Always discuss your specific treatment plan with your oncology team to understand what to expect.

Types of Immunotherapy and Their Side Effect Profiles

Checkpoint inhibitors are the most widely used immunotherapy class in the UK and carry the greatest risk of immune-related alopecia areata, classified as uncommon or rare; CAR-T and targeted therapies have distinct profiles and generally do not cause direct hair loss.

Immunotherapy is not a single treatment — it encompasses several distinct drug classes, each with its own mechanism of action and side effect profile. Understanding these differences helps clarify why hair loss risk varies between patients.

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Checkpoint inhibitors are the most widely used immunotherapy agents in the UK. They block proteins such as PD-1, PD-L1, or CTLA-4 that normally prevent the immune system from attacking cancer cells. Drugs in this class licensed for use in the UK include:

• PD-1 inhibitors: pembrolizumab, nivolumab, cemiplimab, dostarlimab

• PD-L1 inhibitors: atezolizumab, durvalumab, avelumab

• CTLA-4 inhibitors: ipilimumab, tremelimumab (used in combination with durvalumab)

These agents are associated with immune-related adverse events affecting the skin, gut, lungs, liver, and endocrine system. Skin-related irAEs — including rash, vitiligo, and occasionally alopecia areata — are among the more frequently reported. According to MHRA/emc SmPCs and published pharmacovigilance data, alopecia areata occurs in a small minority of patients on checkpoint inhibitors, generally classified as uncommon (occurring in fewer than 1 in 100 patients) or rare, though rates vary by agent and tumour type.

CAR-T cell therapy, used in certain blood cancers, does not typically cause hair loss directly. However, patients almost always receive lymphodepleting conditioning chemotherapy (such as cyclophosphamide and fludarabine) beforehand, and it is this chemotherapy — not the CAR-T cells themselves — that is responsible for any associated hair loss.

Monoclonal antibodies used in targeted therapy — such as trastuzumab (Herceptin) for breast cancer or cetuximab for colorectal cancer — are sometimes loosely grouped with immunotherapy in general discussion, but in NHS and MHRA terminology these are classified as targeted therapies rather than immunotherapy. They generally do not cause alopecia, though some (such as EGFR inhibitors) can affect hair texture.

Interferon and interleukin-based therapies, older forms of immunotherapy now less commonly used, have been associated with hair thinning in some patients. Overall, the side effect profile of immunotherapy is markedly different from chemotherapy, and patients should not assume hair loss is inevitable when starting these treatments.

Managing Hair Changes During Immunotherapy Treatment

Management depends on the underlying cause; reversible factors such as thyroid dysfunction are excluded first, and alopecia areata linked to checkpoint inhibitors is managed using irAE grading principles, with dermatological treatments or systemic corticosteroids in more severe cases.

If you do experience hair changes during immunotherapy, the approach to management will depend on the underlying cause and severity. Because hair loss linked to immunotherapy is most often immune-mediated rather than chemotherapy-related, the management strategies differ significantly.

Before attributing hair changes solely to a direct irAE, your clinical team will consider reversible contributing causes. These include thyroid dysfunction (particularly hypothyroidism, a recognised irAE of checkpoint inhibitors) and nutritional deficiencies. Blood tests such as TSH and, where clinically indicated, ferritin, vitamin B12, or vitamin D may be checked.

For alopecia areata linked to checkpoint inhibitors, management follows irAE grading principles as set out in UKONS Immunotherapy Toxicity Management Guidelines and ESMO/ASCO irAE management guidance, alongside dose-modification advice in the relevant MHRA/emc SmPC. In mild cases, immunotherapy does not usually need to be interrupted. Dermatological treatments for alopecia areata — such as topical corticosteroids or intralesional steroid injections — may be considered in line with British Association of Dermatologists (BAD) guidance. In more severe cases, systemic corticosteroids or temporary dose modification of the immunotherapy may be recommended following multidisciplinary team (MDT) discussion.

General hair and scalp care during immunotherapy treatment includes the following supportive measures:

• Using gentle, sulphate-free shampoos and avoiding harsh chemical treatments

• Minimising heat styling and tight hairstyles that place stress on hair follicles

• Keeping the scalp moisturised if dryness or irritation develops

• Wearing sun protection on the scalp if hair thinning occurs

It is worth noting that scalp cooling (cold cap therapy), which is used to reduce chemotherapy-induced hair loss, is not relevant for immunotherapy-related alopecia, as the mechanism of hair follicle damage is entirely different.

Emotional and psychological support is equally important. Hair changes, even when mild, can significantly affect body image and wellbeing. Many NHS cancer centres offer access to hair loss counselling, wig fitting services, and support groups through their allied health professional teams. Macmillan Cancer Support and the charity Alopecia UK also provide practical guidance and peer support for those experiencing treatment-related hair changes.

When to Speak to Your Oncology Team About Hair Loss

Contact your oncology team promptly if hair loss is sudden, patchy, accompanied by rash or systemic symptoms, or emotionally distressing, as these may indicate a significant irAE requiring early assessment.

Knowing when to raise concerns with your oncology team is an important part of safe cancer care. Not all hair changes during immunotherapy require urgent attention, but some warrant prompt assessment to rule out a significant immune-related adverse event.

Contact your oncology team, clinical nurse specialist, or 24-hour acute oncology helpline if you notice:

• Sudden or rapidly progressing hair loss, particularly in patches

• Hair loss accompanied by skin rash, redness, or scalp inflammation

• Hair loss alongside other new symptoms such as fatigue, unexplained weight change, cold intolerance, constipation, joint pain, or changes in bowel habits — which could suggest a broader irAE, including thyroid dysfunction

• Significant emotional distress related to hair changes that is affecting your daily life

Most NHS oncology units provide a dedicated 24-hour helpline for patients on immunotherapy. You should use this number for any new or worsening symptoms that concern you, rather than waiting for your next scheduled appointment.

It is also important to report hair loss even if it seems minor. Immune-related adverse events can sometimes be early indicators of more significant systemic immune activation, and early identification allows the team to monitor and intervene before problems escalate. Patients and healthcare professionals can also report suspected side effects of immunotherapy agents to the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or via the Yellow Card app, contributing to ongoing pharmacovigilance.

Your oncology team may refer you to a consultant dermatologist if alopecia areata is suspected, as specialist input can help confirm the diagnosis and guide treatment. In most cases, hair loss associated with immunotherapy is manageable and may be reversible once treatment is completed or adjusted — unlike some forms of chemotherapy-induced alopecia, which can occasionally be permanent.

Always be open with your team about any changes you notice, however small they may seem. Shared decision-making is central to NHS cancer care, and your concerns are always valid.

NHS Support and Resources for Cancer Treatment Side Effects

NHS cancer care teams, Macmillan Cancer Support, Alopecia UK, and Cancer Research UK all provide specialist support for immunotherapy side effects, including hair loss, with 24-hour helplines and holistic needs assessments available.

The NHS provides a broad range of support services for people experiencing side effects from cancer treatment, including those related to immunotherapy. Knowing where to turn can make a meaningful difference to your experience and quality of life during treatment.

Key NHS and UK resources include:

• NHS Cancer Care Teams: Your named clinical nurse specialist (CNS) is often the first point of contact for side effect concerns between appointments. Most oncology units provide a dedicated 24-hour helpline number — keep this to hand throughout your treatment.

• Macmillan Cancer Support (macmillan.org.uk): Offers comprehensive information on immunotherapy side effects, financial support, and emotional wellbeing resources, including a free helpline (0808 808 00 00).

• Cancer Research UK (cancerresearchuk.org): Provides evidence-based patient information on immunotherapy treatments and their side effects, written in accessible language.

• Alopecia UK (alopecia.org.uk): A specialist charity offering support specifically for people experiencing alopecia, including treatment-related hair loss.

• MHRA/emc (medicines.org.uk/emc): The primary UK source for approved product information (SmPCs) for all licensed immunotherapy agents, including detailed summaries of known side effects and dose-modification guidance.

Within the NHS, NICE technology appraisals (TAs) determine which immunotherapy treatments are recommended for NHS use in England. The monitoring and management of treatment side effects follows MHRA-approved SmPCs, UKONS Immunotherapy Toxicity Management Guidelines, ESMO/ASCO irAE guidance, and local Acute Oncology Service pathways — rather than a single NICE irAE guideline.

Many NHS Trusts also offer holistic needs assessments (HNAs) at key points during cancer treatment. These structured conversations with a healthcare professional help identify physical, emotional, and practical concerns — including those related to appearance and hair loss — and connect patients with the right support services. If you have not been offered an HNA, you can ask your CNS or oncology team about accessing one. You do not need to manage the side effects of cancer treatment alone.

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