"My chest is fine, so the inhaler can wait"

Asthma is the cleanest case of the holding ones, because the two inhalers look alike and do opposite jobs. The reliever, the NHS explains, is for when you get symptoms. The preventer is for every day, to stop the symptoms happening, and the NHS is explicit that you shouldn't be given a blue reliever to use on its own. Some people now have a single inhaler that does both jobs, and the instructions for those come with the inhaler. But the reader with two inhalers who uses the preventer only when the chest is tight has turned it into a second reliever, and it's a poor one, because that's not what it does.

The study I mentioned in chapter 3 is the one to hold onto here. Of 405 adults with asthma in one American health system, adherence to preventer inhalers ran at about half. Each 25 percent increase in the time spent without the preventer doubled the rate of asthma hospital admissions. The researchers estimated that if there'd been no gaps in use, about 60 percent of the admissions in the study period wouldn't have happened. Those admissions came from people whose chests were fine right up until they weren't, which is what asthma does.

The feeling-fine test fails here in a specific way. A well-controlled chest feels like a chest that doesn't need anything. It feels that way because of the preventer. Stop, and for days or weeks the feeling continues, because inflammation builds slowly. Then a cold or a cold morning or a cat arrives, and the reliever is being used three times a day, and the NHS says that needing your inhaler more often is a reason to see a GP. The fine chest and the bad night are the same story with a gap in the middle, and the gap was the preventer in a drawer.

The NHS says you should have a check-up at least once a year and that it will include checking you're using your inhalers correctly. That's a conversation with a nurse who's heard "I only use it when I need it" a thousand times and can explain, without any disapproval, why the sentence has the medicines the wrong way round.