你的微笑为何让我感冒
[nĭ de wēi xiào wéi hé ràng wŏ găn mào]
"Why does your smile give me a cold?" It's actually using the concept of having 'a cold' as a metaphorical expression which could mean being captivated, mesmerized, enchanted by someone else’s beautiful or endearing smile. It's also a witty and light-hearted way to say one feels emotionally touched by the sight.