Stevens-Johnson syndrome is a rare but severe reaction, usually triggered by medications, that causes painful skin blistering and peeling, as well as damage to the mucous membranes. It often begins with flu-like symptoms and can progress rapidly, sometimes leading to life-threatening complications. In more severe cases, where over 30% of the skin is affected, it becomes Toxic Epidermal Necrolysis (TEN). Early medical intervention is critical to managing the condition.