Based on PubMed | Can radiation or chemotherapy for head and neck cancer cause hair loss, and is it usually temporary or permanent?

Hair loss can happen with both radiation therapy and chemotherapy used for head and neck cancers, but the pattern and likelihood of regrowth differ by treatment type, dose, and where the treatment is delivered. Most chemotherapy-related hair loss is temporary, while radiation to the scalp can sometimes cause permanent hair loss depending on dose. ^{[1] [2]}

How chemotherapy causes hair loss

Chemotherapy targets fast‑growing cancer cells, but it also affects fast‑growing normal cells such as hair follicle cells, which can lead to thinning or complete hair loss on the scalp and sometimes on eyebrows, eyelashes, and body hair. Hair loss typically starts 1 to 4 weeks after the first chemo cycle, and most shedding happens by 3 to 6 weeks. ^{[1] [3]} In the majority of cases, hair regrows after chemo stops, usually beginning within 3 to 5 months, though texture or color may change. ^[2] A small number of people can have long‑lasting or persistent thinning, but truly permanent loss after standard chemo is uncommon. ^[4]

• Timing: Shedding often begins within 1–4 weeks; most by 3–6 weeks after start. ^{[1] [3]}
• Regrowth: Starts after treatment ends, usually 3–5 months; hair may come back different. ^{[5] [2]}
• Extent: Depends on drug class, dose, and schedule; higher doses and certain combinations cause more hair loss. ^[6]
• Persistence: Rare cases of permanent alopecia have been reported, more often with high‑dose regimens or transplant conditioning. ^{[2] [7]}

How radiation causes hair loss

Radiation causes hair loss (radiation‑induced alopecia) by damaging hair follicles within the field treated. Hair loss from radiation usually occurs only in the area that receives radiation, such as parts of the scalp within the beam path for head and neck treatments; exit-dose paths can also create patchy loss (for example, the back of the head during nasopharynx treatment). ^[8] Radiation‑related hair loss typically starts about 2–4 weeks after the first session. ^{[1] [9]}

Whether hair regrows after radiation depends largely on the dose delivered to the hair follicles. Lower follicle doses may allow regrowth, but higher doses can lead to patchy or permanent hair loss. ^[10] There is a small but real chance that hair may not grow back after radiation to the head, and when it does, it might be thinner or different in texture. ^{[5] [11]}

• Timing: Hair thinning or loss begins around 4 weeks after starting radiation. ^[1]
• Location: Confined to treated areas or exit paths of the beam. ^[8]
• Dose effect: Permanent alopecia risk rises with higher follicle dose; modern techniques aim to spare skin and hair when feasible. ^[10]

Temporary vs. permanent: what’s typical?

• Chemotherapy: Usually temporary with regrowth within months after therapy ends. ^{[2] [5]} Permanent loss is rare but documented, particularly with high‑dose or transplant‑related regimens. ^{[7] [12]}
• Radiation therapy (to the head/scalp): Can be temporary or permanent; the risk of permanent loss increases with higher doses to hair follicles. ^{[5] [10]} Outside the scalp (e.g., neck fields not touching hair), radiation does not cause scalp hair loss. ^[8]

When does hair start to fall out and regrow?

• Start of loss: Chemo 1–4 weeks; radiation about 4 weeks. Most shedding peaks within the first 1–2 months of treatment. ^{[1] [3]}
• Regrowth: Commonly begins 3–5 months after treatments stop for chemo; radiation regrowth is variable and dose‑dependent. ^{[2] [5]} Regrown hair may look or feel different. ^[5]

Practical tips to cope and support regrowth

• Gentle hair care: Use mild, fragrance‑free shampoo and conditioner, wash every 2–4 days, pat dry, and brush gently with a soft‑bristle brush. Avoid bleaching, perming, or harsh treatments during therapy. ^{[13] [14]}
• Shorter styles or wigs: Consider cutting hair short before treatment and explore wigs or head coverings to ease the transition. Products that camouflage thinning can help confidence. ^[15]
• Scalp cooling during some chemotherapies: Cooling caps can reduce chemo‑related hair loss for certain drug regimens, though results vary and they do not prevent radiation‑related hair loss. Long‑term protection against persistent alopecia is not established. ^[16]
• Expect changes: It’s common for regrown hair to have a different texture or color. ^[5] Discuss your specific regimen and radiation field with your care team to understand your individual risk. ^[1]

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Summary table: hair loss by treatment type

Feature	Chemotherapy	Radiation therapy to head/scalp
Onset of hair loss	1–4 weeks after first cycle; peak by 3–6 weeks [1] [3]	Around 4 weeks after starting; within 2–3 weeks of first dose in many cases [1] [9]
Areas affected	Scalp and sometimes brows, lashes, body hair [11]	Only in treated scalp areas or beam exit path [8]
Typical outcome	Regrowth in 3–5 months after completion; texture/color changes common [2] [5]	Regrowth depends on dose; high doses can cause permanent or patchy loss [10] [5]
Permanent risk	Uncommon; reported in high‑dose/conditioning settings [7] [12]	Small but real risk, higher with greater follicle dose [10]
Prevention	Scalp cooling may reduce loss for some regimens; variable efficacy [16]	No proven method to prevent radiation‑induced alopecia [16]

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Key takeaways

• Yes both chemotherapy and radiation for head and neck cancer can cause hair loss. ^[1]
• Chemotherapy‑related hair loss is usually temporary with regrowth in months. ^[2]
• Radiation to the scalp can lead to temporary or, at higher doses, permanent hair loss in treated areas. ^{[5] [10]}
• Timing varies, and individual risk depends on the specific chemo agents, doses, and radiation fields. ^{[6] [1]}

If you’d like help estimating your personal likelihood of regrowth, sharing your exact chemotherapy drugs and whether any part of your scalp was within the radiation field would be useful.