LOS ANGELES (CBSLA.com) — NCIS actress Pauley Perrette is warning fans about the dangers of hair dye after suffering a severe allergic reaction to her trademark ink-black color.

KCAL9’s Kristine Lazar spoke with Perrette, whose character, Abby Sciuto, is known for her raven locks.

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A natural blonde, the actress has been dying her hair for 20 years.

But her beauty routine landed her in the hospital when she broke out in a rash and began to experience severe swelling.

“The other half of my face had become twice the size of my head,” she said.

Perrette posted a photo of her swollen face on social media, warning her half-million Twitter followers about the dangers of hair-dye allergies.

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“The most important thing to me is that anyone out there that dyes their hair, particularly black, you need to be aware of the symptoms,” she said.

There are warning signs, according to Jacob Offenberger, an allergist at Northridge Medical Center.

“If you have hair dye, and the next day or the day after you start to have itchiness and you start to see redness or [an] eczema-type of lesion, it is telling that you that you are having an allergic reaction to that dying,” Offenberger said, warning, “If you would do nothing, the next time you do the hair dye, it’s going to get worse.”

That is exactly what happened to Perrette.

Six months ago, the actress broke out into a rash all over her neck and scalp but ignored the symptoms, she said.

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Perrette says she’s now looking into natural hair dye and also into wearing a wig.