The 45-year-old former child star – who appeared on the reality show in 2013 – is recovering from emergency neuro surgery at the Heath Hospital in Wales.
Harries' mother tweeted: "Please help: Lauren has had a number of blackouts after which the right side of her face droops. This is incredibly scary for Lauren and us. She also has a consistent headache.
"Drs haven't been able to explain what is causing these. Have you or someone you know been through this? Any ideas or help you could give will be so helpful. @NHSuk have saved Lauren but they can't find any answers for this and it is so scary when it happens, it happened again yesterday. Please help find out what's causing these!"
The reality star rose to fame as 12-year-old precocious antiques expert James Harries appearing on BBC chat show Wogan and the Antiques Roadshow in the 1980s.
She underwent gender reassignment surgery in 2001 and came third on the 12th series of Celebrity Big Brother on Channel 5 in 2013.
Her mother Katy revealed she had undergone emergency brain surgery on Friday 14 April and asked fans to pray for her.
A day later she revealed Harries was awake and shared a picture of her smiling, despite having to undergo her "worst nightmare" of having her head shaved.
She further updated that Harries was suffering memory loss and headaches while in recovery.
Katy has thanked fans for their "prayers, good wishes and flowers" and revealed Harries is due to undergo physiotherapy as part of her recovery.
Thank you for your prayers & good wishes and cards & flowers! Lauren is still recovering from neurosurgery, & a chest and throat infection. Lauren would also like to thank the NHS Nurses & Doctors. Physiotherapy next, while she is fighting a permanent headache. 'Peace and light' pic.twitter.com/5Th5iZOrOs
— Lauren Harries (@LaurenHarries) May 2, 2023
Harries has been a guest antiques expert on This Morning, as well as appearing on Celebrity Juice, Loose Women and Naked Attraction.
Speaking about appearing on CBB she said in 2015: "The three weeks I spent on Celebrity Big Brother really enlightened people to who I am. They realised I was not the freak the press had depicted.
"Now fans approach me with love and for that I feel blessed."
Watch: AJ Odudu and Will Best will host a Big Brother UK reboot on ITV