The Oscar-winning actress Lupita Nyong’o has spoken over the years about her struggles to learn to love her hair and skin color. She was taunted as a young girl for her “night-shaded skin,” she has said. She once felt “unbeautiful.”Finally, Ms. Nyong’o said she realized that beauty was not a thing that she could acquire or change. “It was something that I just had to be,” she said at a Black Women in Hollywood luncheon in 2014.

But now, at 34, Ms. Nyong’o has yet again found herself defending that beauty.On the cover of its November issue, the magazine Grazia UK featured an altered image of Ms. Nyong’o. Gone is her mass of curly black hair, held in a thick ponytail at the back of her neck in the original photograph.

On Instagram, in a post that was widely viewed and shared, Ms. Nyong’o rejected the magazine’s use of the image.

As I have made clear so often in the past with every fiber of my being, I embrace my natural heritage and despite having grown up thinking light skin and straight, silky hair were the standards of beauty, I now know that my dark skin and kinky, coily hair are beautiful too.

Being featured on the cover of a magazine fulfills me as it is an opportunity to show other dark, kinky-haired people, and particularly our children, that they are beautiful just the way they are.

I am disappointed that @graziauk invited me to be on their cover and then edited out and smoothed my hair to fit their notion of what beautiful hair looks like. Had I been consulted, I would have explained that I cannot support or condone the omission of what is my native heritage with the intention that they appreciate that there is still a very long way to go to combat the unconscious prejudice against black women’s complexion, hair style and texture.

Ms. Nyong’o affixed the hashtag #dtmh, the acronym for the song “Don’t Touch My Hair,” by Solange Knowles. The London Evening Standard magazine apologized to Ms. Knowles last month for removing a significant portion of her hair from an image that appeared on the cover of its October edition.

In September, the hip-hop artist Nicki Minaj called out magazines for altering her hair while not doing the same to women of other races. “For years, fashion mags would change my hair for their covers but allow women of a diff race to wear the exact style on the cover,” she said on Twitter.

On Friday, Grazia magazine issued a statement apologizing to Ms. Nyong’o but deflecting blame for the image alteration.