The reality star-turned-fashion designer hit back via Twitter after critics poked fun at a recent promotional photo showing Olivia and Alex kissing for the camera while holding packets of condoms.
Reacting to the post, which generated more than 1,300 comments, Olivia, 23, said: "To people who cannot fathom WHY I am working with Superdrug on their Christmas Condom Campaign, there's an importance to the silliness."
Olivia continued: "I am extremely proud that Alex and I have had the chance to support and raise awareness about being safe with sex. Why wouldn't I want to help spread a message of health to people?
"I'm lucky enough to have a large following on Twitter and on Instagram, and that gives me a huge ability to reach out to a large audience about a serious subject."
Olivia also shared some facts about sexually transmitted diseases, saying: "Around 8,000 people are diagnosed with HIV in England every damn year and in 2015 there were 434,456 new STI diagnoses. Let that just sink in for a moment."
The star concluded: "It's clear it needs to be spoken about more, as some of you seem scared and offended by it. WISE UP. YOU ARE NOT INVINCIBLE."
Olivia found fame on this summer's Love Island, where she met boyfriend Alex. They've now moved in together in Essex.
Most recently, Olivia has launched a clothing line with Quiz.
Like this? Don't miss out! Make sure you're following Reveal across Twitter @RevealMag / Facebook @Revealmagazine / Instagram @revealmagofficial