Moisture in the air increases the number of mould spores, which is why wet autumns create a particular problem. The moment that a mould spore lands on the moist lining of the nose, eye or airways, the allergen begins to leak out of the spore, causing symptoms such as non-stop sneezing. Avoid certain gardening activities, such as raking rotting leaves or composting, as these can disturb mould spores.