Sources have claimed to TMZ that the 54-year-old actor was admitted to a Los Angeles hospital in late March, but a reason is yet to be revealed.
A representative for the Vacation star told the outlet: "I have no comment whether she is in the hospital or what her medical treatments are.Â
"She's had a long history of complicated medical conditions that she has been refreshingly open about, as evidenced in her memoir and on her podcast."
In June 2021, Applegate first announced her battle with MS - an incurable chronic autoimmune disease that impacts the brain and spinal cord.
And in March 2025, the Married... With Children alum revealed she ended up in hospital more than 30 times with "unimaginable" pain with her MS, which can cause issues including muscle weakness, vision changes and numbness.
Speaking on her MesSY podcast, she explained: "This is really important because for three years, since I was diagnosed, I've been in the hospital upwards of 30 times from throwing up, diarrhoea and pain that is unimaginable.
"They've done every test known to man on me, put so much radiation into my body from CT scans to everything else."
Applegate urged her listeners to get checked out over certain issues, and she described the problem as being like every organ in the body was fighting with the other.
In February 2026, Applegate - who has a 15-year-old daughter called Sadie with her 57-year-old husband, Porno for Pyros bassist Martyn LeNoble - shared she is largely confined to her bedroom because of her MS battle.
In March, Applegate revealed she bought a final resting place for herself and two other people in a "really pretty" spot because she has regularly thought about death since her diagnosis.