Velno’s Vegetable Syrup

Isaac moved to London where he served as assistant to a Dr. Mercier in Frith Street, Soho, where he settled. Later, he purchased from Dr Mercier the recipe of a patent medicine called "Velnos’ Vegetable Syrup", named after Vergery de Velnos. This was one of many cures for venereal diseases based on vegetables rather than mercury, which is extremely toxic. This brand became well-known and Isaac Swainson reputedly made as much as £5,000 a year from its sales. In addition to curing various venereal diseases, including “the pox” and the “French disease”, it was claimed to cure leprosy, gout, scrophula, dropsy, small pox, consumption, tape worms, cancer, scurvy, and diaorrhea

Whether he believed in the efficacy of his remedy or not, he did study the conventional medicine of the era and gained an MD in 1785, although there is no record of his subsequent election to the Royal College of Physicians. .

He wrote several commercial pamphlets advocating the efficacy of Velno's Vegetable Syrup under titles such as, An account of cures by Velno's vegetable syrup : in disorders deriving their origin or malignity from scorbutic impurities; which occasion obstructions in the lymphatic vessels that also warned purchasers to steer clear of imitations, which were giving the product a bad name.

The Botanical Garden at Twickenham

His profits from his patent medicine left him with sufficient money to take a sizeable estate and operate a botanical garden, which became quite noted in its time. It was located in the Heath Lane Lodge estate in Twickenham, London. Swainson took plants and seeds from many parts of the world.

J C Loudon, a famous contemporary botanist, wrote that

It contained every tree and shrub that could be procured at the time in British nurseries, and was kept in the first style of order and neatness.

His wife died in 1806, while Swainson died on 7 March 1812 at his house in Frith Street, Soho.

Sturt's Desert Pea

It is Isaac Swainson, not William Swainson who was less noted for botany, who is honoured in the genus name Swainsona, the emblem of South Australia. The species was named for him by the botanist George Don.

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