I have similar experience when my boy is 4 months old. He got high fever and red lips only. At the first 2 days of fever, the doctor said he got flu only, but he refused to take milk and water, so the doctor asked me to send him to hospital because worried 'lack of water'. After the hospital checking, they said no flu germs after lab test, guess he got 'Kawasaki' but he had only 2 symptoms. So the hospital doctor asked me to make decision, give '丙種球蛋白' or not, if gave, then he shall bear the name 'patient of Kawashaki' if not gave, then may affect his heart.
At that moment, I have no choice, must give '丙種球蛋白' , his fever disappeared after 2 hours. Luckily, we made decision within 5 days. No influence on his heart at the end. Thanks the hospital and doctors (東區醫院).