Heat summary - Chapter 6: outdoor allergens
This page summarises Chapter 6 of the Health Effects of Climate Change (HECC) report with a focus on the impact of heat on outdoor allergens. This is part of the science and stats section for the hazard: heat.
Applies to England
CCHS navigation menu:
CCHS homepage
Topic: climate-related hazards
Hazard: all climate-related hazards, heat
Part of: heat summary - full HECC report
Key resources for HECC Chapter 6:
- Heat summary - Chapter 6: outdoor allergens
- Chapter 6 full report (pdf)
Heat summary of Chapter 6
Aeroallergens are airborne particles from pollen and fungal spores that can trigger allergies and hay fever.
Hay fever impacts about 20% of the UK’s population, with more adults affected than children.
Climate change is altering the seasonal timings, concentrations, species composition and allergenic potency of pollen. Earlier and longer pollen seasons might increase the symptoms of hay fever and allergy sufferers.
For fungal spores, warmer temperatures earlier in the year as well as more rain could mean an earlier start to the season for lots of spores, with some species expanding their geographic range.
Trees in lower altitudes may produce less pollen due to heat stress, while those in higher altitudes might thrive and produce more pollen under a warmer climate.
It is difficult to make effective policies to reduce the level of fungal spores and pollen, because they occur naturally and vary depending on the season. There isn’t an agreed threshold to decide when the amount of aeroallergens is considered dangerous.
Some policies are in place which help reduce other climate change related hazards, but which make pollen production worse – for example planting trees to remove carbon from the atmosphere and create areas of shade. Actions to combat this include reducing the planting of specific tree species which produce allergenic pollen.
It is likely that pollen potency will increase, and this will enhance the season for hay fever sufferers in most years, although this may decline from the 2030s because of extreme weather events and land-use changes, resulting in a mixed trend.
In the short term, warmer temperatures and pollution interactions are expected to increase pollen potency, leading to continued high levels of seasonal respiratory allergies over the next decade or two, though there might be occasional milder seasons.