It appears Friday was a rough day for actress Selma Blair.

The “Cruel Intentions’ star, who revealed her multiple sclerosis (MS) diagnosis in October, took to Instagram to share a post about her struggles with the medical treatments for the “unpredictable, often disabling disease that disrupts the flow of information within the brain, and between the brain and body," according to the National Multiple Sclerosis Society.

“Here’s a truth. I feel sick as all hell. I am vomiting and all the things which are not polite to speak of. My son ran away. From me. I have to get him to school. The medical treatments take their toll,” she began.

ACTRESS SELMA BLAIR, 46, REVEALS MS DIAGNOSIS: 'I AM DISABLED'

But, Blair said: “I am going to get through this. We do. This will pass. And to moms and dads who watch their kids sick on things we want them to take to get better... I hold you. So glad this is me and not my child.”

She continued: “I cannot imagine ever feeling ok again. #roughday. But it’s still morning. We get through. #realitycheck.”

Blair, 46, received support and sympathy from fellow celebrities.

An error occurred while retrieving the Instagram post. It might have been deleted.

“I’m sorry you’re having a rough day,” actress Jennifer Garner wrote in response.

“[Love] you,” said Kate Bosworth.

“Sending you love and healing. I’m so sorry you’re going through this. Grateful you’re strong and wonderful enough to share your experiences with others. So many people are being helped by your willingness to share your reality,” commented Jaimie Alexander.

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The “Legally Blonde” actress has been open about her struggles with the disease, which symptoms can include fatigue, numbness, pain, walking difficulties, and vision problems, among others, per the National Multiple Sclerosis Society.

In March, Blair took to Instagram with a photo from a trip to Miami, Fla. She revealed it was during the trip that she first experienced early symptoms of MS, though she largely dismissed them at the time.

In April, the actress again took to the photo sharing platform to post a sweet snap of herself and actor Michael J. Fox, who suffers from Parkinson’s and who Blair has said has provided her with invaluable advice on how to cope with a life-altering health condition after working in the entertainment industry, People reported.

Fox News' Jennifer Earl and Danielle Wallace contributed to this report.