It has long been believed in Europe and the United States that a seventh son is especially lucky or gifted with occult powers, and that the seventh son of a seventh son has healing powers. In Scotland, the seventh daughter of a seventh daughter was said to have the gift of second sight (prophetic vision). In Ireland, the saliva of a seventh son was said to have healing properties. However, in Romanian folklore, a seventh child was believed to be fated to become a vampire.
As early as the beginning of the seventeenth century, the Diary of Walter Yonge 1604-1628 (published by the Camden Society, 1847, edited by G. Roberts) had a negative reference to the healing powers of a seventh son:
"In January, 1606-7, it is reported from London by credible letters, that a child being the seventh son of his mother, and no woman child born between, healeth deaf, blind, and lame; but the parents of the child are popish, as so many say as are healed by it. The Bishop of London, Doctor Vaughan, caused divers [various people] to be brought to the child as aforesaid, who said a short prayer as [he] imposed his hands upon, as 'tis said he did unto others; but no miracle followeth any, so that it appeareth to be a plain lie invented to win grace to the popish faction."
Thomas Lupton, in the second edition of his book A Thousand Notable Things (1660), noted, "It is manifest, by experience, that the seventh male child, by just order (never a girl or wench being born between) doth heal only with touching (through a natural gift) the king's evil [scrofula], which is a special gift of God, given to kings and queens, as daily experience doth witnesse."
In France, there was also a tradition that a seventh son had the power to cure the king's evil. He was called a "Marcou" and branded with a fleur-de-lis. The Marcou breathed on the part affected, or else the patient touched the Marcou's fleur-de-lis.
Robert Chambers, in his Domestic Annals of Scotland from the Reformation to the Revolution (1858), stated that in February 1682, a certain Hugh McGie, "… gave in a bill to the Privy Council, representing that, by the practice of other nations, any tradesman having seven sons together, without the intervention of a daughter, is declared free of all public burdens and taxes, and has other encouragements bestowed on him, to enable him to bring up the said children for the use and benefit of the commonwealth; and claiming a similar privilege on the strength of his having that qualification. The Council recommended the magistrates [of Edinburgh] to take Hugh's seven sons into consideration when they laid their 'stents' (trade taxes) upon him."
A tradition in Donegal, Ireland, claimed that the healing powers of a seventh son required a special ceremony at the moment of the infant's birth. The woman who received the child in her arms should place in its hand whatever substance she decided that he should use to heal in later life. This substance could be metal (e.g., a silver coin) or a common substance like salt, or even hair; when the child was old enough, it would rub the substance and the patient would apply it to an afflicted part for healing purposes. There was also an Irish tradition similar to the Scottish belief that a seventh son of a seventh son possessed prophetic as well as healing powers.
There was a general belief in Britain that the seventh son of a seventh son was destined to be a physician and would have an intuitive knowledge of the art of healing, often curing a patient simply by touching an afflicted part. This belief also extended to the seventh daughter of a seventh daughter. A contributor to Notes & Queries (June 12, 1852) observed: "In Saltash Street, Plymouth [England], my friend copied, on the 10th December, 1851, the following inscription on a board, indicating the profession and claims of the inhabitant: 'A. Shepherd, the third seventh daughter, Doctress."'
The belief in the healing powers of a seventh son of a seventh son has persisted into the twentieth century, and there are two Irish healers of this kind: Danny Gallagher and Finbarr Nolan. Both are "touch healers," although Gallagher additionally "blesses" soil that is to be mixed with water and applied to the afflicted area of the patient; both healers recommend a sequence of two or three visits for maximum healing. They are credited with remarkable cures. Gallagher is reported to have restored the sight of a woman blind for twenty-two years, and Nolan claims to have successfully healed injured race horses as well as human beings.
Chambers, Robert. Domestic Annals of Scotland from the Reformation to the Revolution. 2 vols. Edinburgh, 1858.
Lupton, Thomas. A Thousand Notable Things. London, 1660.