Selma Blair urged Christina Applegate to get tested for MS after clocking this symptom

In 2021, Christina Applegate was diagnosed with multiple sclerosis. But that might not have happened without the help of her friend and fellow actor with MS, Selma Blair.

In a recent voice message to British Vogue, Applegate recounted the day Blair urged her to get tested for the disease while their kids were on a play date. Blair, who went public with her own MS diagnosis in 2018, graced the digital cover of British Vogue on Thursday.

"I was sitting in Selma's living room, our children playing, and I told Selma I'd been having this weird tingling in my feet," the "Dead to Me" star recalled.

"She said, 'You must get tested for MS.' ... In essence, because of her I'm going to have a better quality of life."

Even though her "doctor doubted it," Applegate followed Blair's advice, and now both celebrities have become prominent advocates for the MS community.

"I didn't imagine I could ever make a difference by showing up as myself and being open about my experiences," Blair told British Vogue.

"But when others with mobility aids rallied around my presence on the red carpet with a cane and in the midst of an MS flare, I noticed. I felt empowered to share. … Now it's a conscious choice to."

"Sets were excruciating sometimes with the exhaustion and the tics. I took benzos and Klonopin," a medication used to prevent seizures and anxiety disorders. "I didn't abuse those things, just alcohol," she told British Vogue. "But I was lost and sad and could hardly ever smile. Hence my roles, I imagine."

While filming "Hellboy" (2004), Blair was diagnosed with cat scratch fever and possible leukemia — but she didn't dare tell anybody out of constant fear she would be "found out" and "deemed an insurance risk."

"I was worried since the beginning of time that a glaring fault would remove me from the workforce," Blair said. "And usually it was my incoordination or getting stuck, too weak or sick."

"I was always terrified I would be deemed incapable. Or mentally unsound," she added. "My mother taught me that was death for a woman career-wise."

By the early 2010s, Blair's "autoimmune system was misfiring" and she was losing large amounts of hair and energy. She calculated how many naps she could "fit in on the side of the road" while driving to and from auditions.

Since announcing her MS diagnosis and making high-profile appearances with her signature cane, Blair has become a vocal member of the disabled community. She credits her allies in the community with empowering her and helping her move forward, and she has considered making a return to the screen.

"[I think producers] are open to it now," she said.