Flying with a cold or sinus infection

Aircraft cabins are pressurised, but not to sea level. At cruising altitude the cabin sits at roughly the equivalent of 6,000 to 8,000 feet. Two things follow from that, and between them they explain almost every medical restriction airlines impose.

First, there is less oxygen available. A healthy passenger’s blood oxygen saturation typically drops a few percent — unnoticeable if your heart and lungs are working normally, much less so if they are not. Second, trapped gas expands by around a third. Any pocket of air sealed inside the body — in the middle ear, the sinuses, the bowel, the chest, under a plaster cast — gets bigger as the aircraft climbs, and shrinks again on descent.

Where the pain comes from

The sinuses and middle ears are air-filled spaces that connect to the nose through narrow openings. Congestion swells the lining and blocks those openings. Air can no longer move in and out freely, so as the aircraft descends and cabin pressure rises, the pressure outside your sinuses and eardrums exceeds the pressure inside them.

That pressure difference is what produces the pain, and with a badly blocked sinus it can be severe — a sharp, boring pain over the cheekbone or forehead that arrives somewhere over the destination and does not let up until you are on the ground. It is called sinus barotrauma, and it is one of the more genuinely unpleasant experiences available in economy.

What actually helps

• A decongestant nasal spray used shortly before descent is the single most effective measure. Ask a pharmacist — they are well placed to advise, and it is not suitable for everyone
• Stay awake for the descent. You swallow far less asleep, and that is when ears block hardest
• Swallow, yawn, chew or sip steadily throughout the descent
• Gentle Valsalva — pinch your nose, close your mouth, blow softly. Gently
• Hydrate. Cabin humidity is very low, which thickens secretions
• For babies, feed or offer a bottle or dummy during the descent