Foster opened up about her struggle with the disease, a bacterial infection that is spread through a tick bite.
"I wasted the first year trying to get diagnosed and spent the next two trying to find a cure," said Foster, who was diagnosed in 2012. "I have gone from the conventional long-term antibiotics to about every holistic protocol there is to offer. Unfortunately, I was only able to get to about a 60 percent recovery until I relapsed in early December and have not been able to find my way back."
Besides a couple passing references, Foster's ongoing battle with Lyme disease has gone largely unmentioned in the current season of "Real Housewives." But she was candid in her blog post.
"The most frustrating thing is that there is medical data on Lyme and spirochete infections going back all the way to 1908, but yet we still don't have proper diagnostic testing, a vaccine, or a cure for Lyme disease while we are living in the United States of America, the most extraordinary country in the world," Foster wrote.
"Something doesn’t add up here, and I will made it my life mission to figure this out, because nobody deserves to suffer this way in 2015. Unfortunately, I am of no use to anyone or anything at this moment while weathering the storm," she said.
Foster said despite having found no cure she has "faith that I will."
In the meantime, the former model, who is married to composer David Foster, is relying on the "unwavering support of my husband, my children, and a handful of true friends," she said, adding how grateful she is for the messages of support she has received on social media.