(KPIX 5) — Fans of the popular NCIS series may be surprised when a regular character shows up with a new hair-do, but it’s not just a fashion choice.

Abby Sciuto, whose goth-black hairstyle has been a trademark for her character could begin season 12 as a blonde, due to an allergic reaction to hair dye.

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Actress Polly Perrette, who plays Sciuto had a bad reaction to the dye after a decade of using it. Her natural hair color is blonde.

Perrette tweeted a picture from a hospital bed, saying “My head swelled up like a huge melon,” while warning that people should “Know the symptons. It can be fatal.”

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Season 12 of NCIS hasn’t started filming. The actress could end up wearing a black wig, or sporting her natural blonde locks.