These relax the very same muscles that cause snoring and also dehydrates the body, leaving nasal passages blocked up.

他们恰好就会使影响打鼾的那块肌肉放松，也会导致身体脱水以及鼻腔阻塞。

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Also consider long-acting decongestant sprays or tablets, which help keep blocked nasal passages open when cabin pressure changes during take-off and landing. (Decongestant can be overly drying in airplane cabin air so consider saline solution, too).

BBC: The flu is a frequent traveller