Hair loss is usually permanent when the scalp is exposed to radiation doses exceeding how much?

Hair loss, or alopecia, resulting from radiation therapy is influenced significantly by the dose of radiation received by the scalp. When the scalp is exposed to higher doses of radiation, the likelihood of permanent hair loss increases.

At doses approaching or exceeding 60 Gy, the damage to hair follicles becomes more severe and is more likely to be irreversible. This is because radiation can cause significant cellular damage to the hair follicle stem cells, which are crucial for hair regeneration. The threshold for permanent alopecia is typically recognized at around this high dose due to the amount of damage it inflicts, disrupting the normal hair growth cycle and making it difficult, if not impossible, for hair to regrow.

In contrast, lower doses can lead to temporary hair loss as the follicles may recover once the radiation treatment is completed. Therefore, understanding the relationship between radiation dose and the risk of permanent hair loss is crucial for both planning treatment and setting appropriate patient expectations.