It happens to my son too when he was about 2-3 months' old. It was called Branchial Fistula (先天性腮漏管). He had it in both sides of his neck. There was some milky stuff, which was the mixture of milk and secretion, coming out and he got inflammed from time to time. He went to see a private doctor and was advised that he should have the operation asap. It is becos if he easily got inflammed, the toxic will easily transmit to the other organs easily and which was very harmful to his body.
He did the operation by a private doctor rather the government doctor as there was a long queue. He had the operation in Jan this year when he was about 5 months' old.
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