Woman's viral photo of sunburn blisters serves as a very cautionary tale

WARNING: GRAPHIC IMAGERY BELOW.

You've heard it before, and you'll hear it again. The sun can cause immense damage to your body each and every day -- but you have to be especially careful during the summer months, when "the days are longer, the sun is stronger," says the American Cancer Society.

But if you needed a reminder, one Twitter user's graphic photo serves as a dire warning to many of us basking in the summer heat. Seriously, guys, do not mess with the summer sun.

According to her Twitter profile, Julie Nesbet, from England, has completed 11 marathons over the past 9 years. An avid athlete, Nisbet felt relatively confident about her most recent endeavor, an ultramarathon consisting of 69 miles.

The mother of two embarked on the 21-hour competition at 7 in the morning, without applying any sunscreen, but stopped at a few hours later to apply SPF 30 . But at the next stop, mile 27, she felt her legs burning -- and she merely reapplied.

"It was only 10 a.m., and the sun wasn't too high in the sky, so at that point I still felt OK," she told BuzzFeed. It was only at the end of the race that she realized her sunburn was much more "intense" than she thought -- blisters were starting to form.

Nisbeth visited urgent care for bandaging, returning the following day for a checkup -- but her small blisters had turned into something much, much more painful.

According to BuzzFeed, at day 3, urgent care drained her blisters and applied fresh bandages. Her "pain was pure agony", understandably, but she had to keep the bandages on for the next few weeks.

"The healing process has been painful — the burning and throbbing as the blisters have filled was a horrendous experience. The pressure in my legs when standing/walking has been also been agonizing at times," she told Buzzfeed.

According to WebMD, her sun blisters were probably indicative of a second-degree burn. "Blisters may mean that deep skin layers and nerve endings have been damaged," the website states, thus taking longer to heal.

As for Nisbeth, she won't make this mistake again. "I'm under no illusion of how negligent I was...It's been a harsh lesson to learn," she said to BuzzFeed. You can read her full story here.

h/t Buzzfeed

Related: Sunscreen we're wearing this summer