Sharing a pic of Rocky wearing a hospital wristband and a bandage on his left index finger, Gellar revealed she "made it seven years" before she had to take one of her children to the emergency room.
"I think that's a pretty good stretch," she exclaimed. "It was a long night and apparently a nasty virus, but thankfully Rocky was released."
"I'm not going to lie, watching your child not be able to breathe, is the most helpless I have ever felt," she continued. "Thank you to all the great doctors and nurses (and staff) who work tirelessly 24 hours a day to help."
The Cruel Intentions star also took to Twitter on Friday, writing, "Thank goodness for #iphones and #inspectorgadget when your little one is sick in the ER. (He's better and resting at home now #nastyvirus)."