A few days before spotting the rash, Karen McGregor saw a Facebook post that highlighted the symptoms of the disease - a post that she said has potentially saved her son's life.
With knowledge that the spots could be a symptom of Lyme disease - a form of arthritis caused by bacteria that are transmitted by ticks - McGregor took her son straight to hospital where her suspicions were confirmed by doctors.
She shared her story on Facebook on 20 June and urged people to share the post in the hope it could help another parent out.
Her post has been shared more than 148,000 times in five days.
McGregor's son was immediately taken to the doctors, given antibiotics and is currently recovering.
On the post she wrote: "I am so grateful for the post similar to this one that I saw three days ago… a post that potentially has saved my son's life."
Explaining what happened, she wrote: "Yesterday I noticed a spot on his temple that looked a lot like a bullseye – the bullseye I had seen in a post about a little girl who was diagnosed with Lyme Disease.
"I phoned our doctor as soon as they opened yesterday and got him in quickly. Within a few hours, more and more of these bullseye spots were showing up on his face, legs and arms."
The mother said she later went to the children's hospital for a check-up, and was told the stage of her son's rash indicated it would have been from a tick bite three to four weeks ago.
"I encourage everyone to watch for these spots!" she wrote.
"They look just like a bullseye, and had it not been for the post I read, I never would have known it was something more than a simple rash caused by being the long grass!
"We are now waiting and hoping and praying that nothing else comes of this. The list of things we are watching for is scary – not a list I ever expected to have to watch my kids for, but I am grateful for the fact that we likely caught this in time!"
At the end, McGregor urged parents to share the post.
Parents have expressed their thanks to McGregor for sharing the posts.
One woman said: "I've literally seen half the people on my friends list share this. So I would say you've done a great job at making people aware."
According to the NHS, It's estimated there are 2,000 to 3,000 new cases of Lyme disease in England and Wales each year, and about 15% of cases occur while people are abroad.
Lyme disease can often be treated effectively if it's detected early on. But if it's not treated or treatment is delayed, there's a risk you could develop severe and long-lasting symptoms.