She told MailOnline today she had booked the holiday after suffering a bad flare-up triggered by tonsillitis. "I know the sun is the best thing for my skin and so booked a mini-break to read and relax."
Speaking to the Evening Standard last night, she said: "I've just been stopped in Portugal checking in to the easyJet flight from Faro back to London before boarding the plane. The boarding desk clerk just stopped and indirectly asked my friend, not me, whether I had a problem with my face or skin.
"Wearing no make-up coming back from holiday - the one thing that helps my skin - I felt great, and my psoriasis has completely gone down, and he actually stopped me.
"I said, 'Excuse me, you should be asking me directly if you think there is something wrong.' He said it's a health and safety procedure. It was completely unacceptable, rude and unprofessional."
She said today: "I understand there are some health conditions where you can't travel. It's how he questioned that I'm angry about. He should have explained the health and safety issue and also asked me first, not my friend. It really was unpleasant and pathetic."
Psoriasis, which affects around three per cent of the world's population, is also linked to an increased risk for depression, heart disease and diabetes, among other conditions.
Ms Dillon is also the founder of the #GetYourSkinOut campaign, which aims to increase awareness of psoriasis and challenge misconceptions.
Speaking to the Huffington Post after it launched last year, she said: "Psoriasis is particularly difficult in summer because when you're in shorts or a dress you'll get these kind of constipated looks on the Tube where people look at your skin like, 'What is that?'
"They don't stop and ask and you can't expect them to, so as well as helping people with psoriasis, this project also aims to answer the questions people are too embarrassed to ask."
She obtained the services of professional photographer Lewis Khan to take pictures of her undergoing PUVA treatment at Chelsea and Westminster hospital.
PUVA, or photochemotherapy, is a type of ultraviolet radiation (phototherapy) used for severe skin diseases
Ms Dillon suffered her first bout of psoriasis at 14 and was later diagnosed with guttate psoriasis.
This is where the skin erupts with small, salmon-pink papules which usually have a fine scale.
More than a decade on, she still suffers regular flare-ups.
In a statement, the airline said: "easyJet is sorry to hear of Ms Dillon's experience while boarding flight EZY2020 from Faro to Luton on Sunday 19 June 2016. As soon as we were made aware this morning, we started an investigation.
"All of our staff are carefully selected and undergo training to maintain our high level of customer care which may not have been upheld in this occasion. We will be addressing this with the ground staff member involved as we always have high standards to maintain. Our customer team is contacting Ms Dillon to discuss this with her directly."
