What does smeared lipstick have to do with cervical cancer?

Why are models like Georgia May Jagger and Cara Delevingne posting smeared lipstick selfies? It's not a fashion statement or the latest bizarre beauty trend, thank goodness. Nope, it's an important, possibly life-saving reminder: Don't forget your Pap smear, ladies!

Called the #SmearforSmear campaign, it was started by a non-profit in the UK called Jo's Cervical Cancer Trust to encourage women to get screened for cervical cancer. Model Suki Waterhouse took it a step further and posted a video.

Pap smears save lives

The test, which involves your doctor performing a simple swab to collect cells from your cervix, is one of the biggest medical success stories. When it was first introduced in the 1940s, cervical cancer was the No. 1 cancer killer of U.S. women. Now it's No. 14. That's because the disease can be successfully treated if the swab reveals any abnormal cellular changes that are the pre-cursor to cancer. In the earliest stages, patients have a 93% survival rate, according to the American Cancer Society, but that drops to 15% for the most advanced stage.

"The number of women taking up their cervical screening invitation in the U.K. is going down year on year and this is extremely worrying," the charity's spokeswoman Maddy Durrant told The Huffington Post. And in the U.S., the numbers aren't much better: A 2014 report from the Centers for Disease Control and Prevention found that 11% of women between 21 and 65 hadn't been screened for cervical cancer in the past five years.

How often do you need a pap smear?

In the past, women would typically have their Pap smear done every year during their well-woman visit, which also includes a routine pelvic and breast exam. But the latest recommendations from the American College of Obstetricians and Gynecologists call for a Pap smear every three years for women between 21 and 29.

Women aged 30 to 65 can have one done every five years if they've had negative Pap smears in the past and if they also receive an HPV test at the same time. (HPV tests are not recommended for women under 30.) If they don't get an HPV test, women aged 30 to 65 should have a Pap smear every three years.

HPV is a common sexually transmitted virus that has about 100 different strains. While some types of HPV cause no symptoms, others cause genital warts, and still others are known as "high-risk" because of their link to certain cancers, namely cervical cancer. (HPV also causes most cases of anal cancers as well as some penile, vaginal, and head and neck cancers.)

If you've had the HPV vaccine, you're not off the hook: you still need regular Pap tests, every three to five years.

Join the campaign and remind a friend

Once you've scheduled your own appointment, spread the love. Apply your favorite shade of lipstick, smear it and snap a selfie. Then, be sure to share it with your friends and followers. Caption the photo with the #SmearforSmear and tag @JoTrust along with the women you love. The goal is for each person who posts a snap with smeared lips to nominate a friend to take one, too.

Following in the footsteps of the ALS Ice Bucket challenge of last summer, Jo's #SmearforSmear campaign is the latest to utilize social media to spread awareness for a healthy cause. The ALS Association raised $115 million to study and fight the disease.

#SmearforSmear is not tied to a research organization, but it's still a creative way to make a difference.

Durrant told The Huffington Post, "Smear tests can prevent women from ever reaching a diagnosis, or can ensure early diagnosis so treatment plans are less extensive and side effects less impactful. Similarly an early diagnosis means a better chance of survival. Quite simply, a smear test could save a woman’s life."