It can be used not just for being physically sick, but also metaphorically for difficult situations, like "I have a headache from this assignment." It's also used when you're tired or have no energy.

In Korea, there's a culture of eating porridge (juk) when sick, so people might send this emoji with the 🥣 (bowl with spoon) emoji. It goes beyond simply conveying that you're sick; it's often used as an emotional expression seeking comfort and concern from the other person.