Taking to Instagram, Gillies shared a photo of a patch of skin underneath her eye, explaining she had been diagnosed with actinic keratosis.
“This is me rocking an Actinic Keratosis. On the left is what it originally looked like. Barely a spot," she wrote.
Actinic keratosis is a growth caused by damage from exposure to UV radiation. If left alone, the precancerous lesion may develop into skin cancer.
In the post, 50-year-old Gillies revealed she had let the spot go untreated for more than a year.
“I ignored it for 18 months because I was frightened of what the treatment would be. Stupid,” she explained.
“I realise the pic on the right LOOKS scary, but that was 2 weeks into treatment. And it was able to be completely covered by makeup. I had no days off work. Even on TV.”
Gillies said she hoped her post would encourage others to seek treatment for any skin concerns.
“I'm sharing these ugly pics so that you know you DON'T necessarily have to get these sunspots 'burnt' off. My treatment was a cream; a kind of 'chemo' cream. My doctor @drnatashacook realised i needed the solution to be the least invasive possible. If ignored, these spots can turn cancerous so I beg you not to wait..like I did,” she posted.
“And now, 5 weeks later? There's not even a mark. Obviously I'm no expert..just a TV chick..but just worth asking the question of your doctor.”