The pressure to look young in Hollywood is intense, even when you're actually young.

In May Kim Kardashian nonchalantly told Nightline she hadn't had any plastic surgery done, but admitted that of course she had used Botox.

Kim's 29.

In January, reality television star and aspiring actress Heidi Montag, 23, was on the cover of People magazine touting the 10 cosmetic procedures she received in one day, including Botox injections.

Other young actresses who have been rumored to have gotten injections include Megan Fox, 24, Lindsay Lohan, 23, Hilary Duff, 22 and Jessica Simpson, 29.

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More and more starlets are feeling the need to start getting Botox injections before their thirtieth, and even twentieth, birthdays to compete with the constant influx of baby-faced newcomers. But of course, no one wants to admit it.

"I don't know why they don't just say they do it, because everyone else does it too. I see maybe four or five well-known actresses a week who insist on coming through the back door because they don't want anyone to see them. And half of those are under 30," says Los Angeles-based cosmetic dermatologist Dr. Simon Ourian, M.D. His youngest Botox injectee? A 17-year old model.

"I think a lot of women feel the pressure to look younger and be at their best. When the rest of the population seems to be younger then you have no choice but to compete," he told FOX411.com.

Botox is a toxin that when used in small doses attaches to nerve endings to prevent the release of neurotransmitters that cause muscle movements. According to the American Society for Aesthetic Plastic Surgery, more than 2.5 million Botox injections were performed in 2009.

There are no significant dangers to starting Botox as a teenager, but starting the injections too early could lead to the treatments not working later in life when these actresses might want to start hiding some more serious wrinkles.

“No long term side effects have been reported. Some studies show that some people develop immunity to it though," explains celebrity plastic surgeon Dr. Michael Fiorello. "Over time Botox doesn’t work as well as it does in the beginning, so after a long time of getting the injections, its doesn’t have the same effect as it did in the beginning."

And casting agents are seeing so many paralyzed pouts that some say they're now specifically seeking out young women who haven't had an abundance of procedures done.

"We want to cast beautiful women. If Botox does that, then good for them. But if I can tell straightaway that an actress has had excessive amounts of Botox treatments, then I will probably move onto the next woman," one casting agent explained. "I don't want to use an actress who doesn't look like a real woman."

Some young women are getting treatments done because of their hard-partying lifestyles.

"If someone told these girls to just get back to basics, don't stay out partying all night, don't drink, don't smoke, and don't do drugs, then they wouldn't need these quick fixes for their face," said casting agent Toni Cusumano.

And it isn't just casting agents who are turning against these Botox babies, its also the fans who see their movies, watch their television shows and buy their products. America wants to see women who are beautiful, but who also have an attainable beauty, explains Cult of Celebrity author Cooper Lawrence.

"These women are not relatable because most Americans at that age are not as vain as New York and Los Angeles twentysomethings are," said Lawrence. "When a twentysomething talks about plastic surgery or Botox, most Americans either roll their eyes or feel pity for the girl for having such low self-esteem. It isn't age appropriate."