Brunettes beware, actress Pauley Perrette has a warning for all those looking to darken their locks.

The NCIS star is thankfully recovering from a beauty scare we should all take note of.

The 45-year-old star who is a natural blonde, dyes her locks a raven color black, but experienced a nasty allergic reaction recently.

We all know Perrette for her Goth-style character on the hit CBS show, and the actress has been dyeing her hair for years, so what happened?

Perrette explained what has been happening to her for nearly a year, sharing the details with her fans via Twitter:

"Wasn't sure if I should tweet about this, but it's important," the actress posted. "Did my head look a bit puffy on the red carpet last night?"

"Turns out I was having a dangerous allergic reaction to hair dye. Been batttling this for a year now, but it gets worse every time," Perrette continued.

"It's an acquired allergy for poeple that dye their hair for years. (Y'all know I'm blonde)."

Check out Perrette in her natural hue below.

The actress even had to be rushed to the emergency room for treatment, as her eye was nearly swollen shut.

"Was in ER. Just got home from hospital. Awful. My head swelled up huge like a melon," Perrette sad. Calling into a local radio station, Perrette revealed that the other half of her face had gotten twice the size of her head! OMG!

So ladies be on the alert, as this condition is in fact common, according to dermatologist Dr. Jessica Weiser.

"You can have it in any hair color, but typically when you see black or dark brown hair dye, you're likely to have a more significant reaction," Weiser told NBC's Extra.

Ever have an allergic reaction to hair dye? Tell us your experience with a not below.