Lewis Spence

“I should add, however, that, particularly on the occasion of Samhain, bonfires were lit with the express intention of scaring away the demonic forces of winter, and we know that, at Bealltainn in Scotland, offerings of baked custard were made within the last hundred and seventy years to the eponymous spirits of wild animals which were particularly prone to prey upon the flocks - the eagle, the crow, and the fox, among others. Indeed, at these seasons all supernatural beings were held in peculiar dread. It seems by no means improbable that these circumstances reveal conditions arising out of a later solar pagan worship in respect of which the cult of fairy was relatively greatly more ancient, and perhaps held to be somewhat inimical.”
― Lewis Spence, British Fairy Origins

“At Bealltainn, or May Day, every effort was made to scare away the fairies, who were particularly dreaded at this season. In the West Highlands charms were used to avert their influence. In the Isle of Man the gorse was set alight to keep them at a distance. In some parts of Ireland the house was sprinkled with holy water to ward off fairy influence. These are only a mere handful out of the large number of references available, but they seem to me to reveal an effort to avoid the attentions of discredited deities on occasions of festival once sacred to them. The gods duly return at the appointed season, but instead of being received with adoration, they are rebuffed by the descendants of their former worshippers, who have embraced a faith which regards them as demons.

In like manner the fairies in Ireland were chased away from the midsummer bonfires by casting fire at them. At the first approach of summer, the fairy folk of Scotland were wont to hold a "Rade," or ceremonial ride on horseback, when they were liable to tread down the growing grain.”
― Lewis Spence, British Fairy Origins