In the cold wet months in the UK with its short days and lower temperatures, people generally spend more time indoors. Within this indoor environment, some allergies tend to worsen in winter.

In clinics or GP practices, general practice nurses (GPNs) may find patients with not well controlled asthma (who may even have exacerbations requiring A& E admission) or chronic rhinosinusitis, which present as persistent hay feverlike symptoms — only to discover that their condition is being triggered by house dust mites.