Briar Houston suffered a 'horrific' sunburn after using a SPF 50+ sunscreen spray.

Melbourne woman Briar Houston enjoyed a few hours at the beach with a friend when she was in Perth for work.

By that night, the 28-year-old was in “a world of pain”.

The entire backs of her legs and her backside were red and she could hardly walk. Her ankles had swollen so much that she could barely see them.

A doctor later told her she had suffered severe first degree burns, and some suspected second degree burns, to 24 per cent of her body surface area.

All this, despite applying (and re-applying after a swim) SPF 50+ sunscreen spray.

"I got the SPF 50+ [spray] to put on my legs and my backside because those are the parts ... I usually forget about and I didn't want to get a burnt bum," Briar told Mamamia.

"I applied it when I got to the beach, then went for a swim and applied it again on my legs. By that evening, I was so red, I had to have a cold shower," she said.

"I've never been burnt like that in my life and it literally came up within three to four hours."

Briar had to seek medical clearance to be able to fly back to Melbourne two days later, and she was prescribed codeine and diazepam for her pain.

"My doctor was very worried about the swelling, she said to me, 'You need to get compression on them, you need to dress them, use this gel and get off your feet'," Briar said.

"She told me, 'If it hasn't gone down or if it doesn't improve within 24 hours you need to go to the burns clinic [at the hospital]."

CEO of Cancer Council Australia, Professor Sanchia Aranda, told Mamamia there are "a lot of issues" with the sunscreen spray products in terms of the way they are applied by many consumers.

"People tend to think about an aerosol [sunscreen] a bit like a mosquito spray," she said.

"You spray it in the general direction and there’s coverage on and therefore you think you'll be protected. When you put other sunscreen on your hand and you rub it on, you get a real sense that you are covered. With the sprays, it's a little bit harder.

"If you’re out there in the sun, the sunscreen can blow away, you might have a fair bit of product coming out but it’s not all going on to your skin."

Professor Aranda recommends those who are using aerosol spray sunscreens to hold the can 15cm away from their skin, and spray for two seconds on each area of the skin.

"That’s actually quite a long time to get the right amount of sunscreen," she said.

While she doesn't recommend avoiding aerosol sunscreens altogether, Professor Aranda does urge that "people be more cautious in how they apply it".

In an interview with the ABC, dermatologist Dr Natasha Cook shared her concerns about spray-on sunscreens.

"I think if we're getting repeated incidents of people having problems using aerosol sprays we really do need to reconsider whether they should be available on the market," she said.