The work of a surgeon aboard ship in the Great Age of Sail was no picnic. Men were more often ill than injured; statistics kept by the Royal Navy on their Jamaica station from the late 18th century until the end of the War of 1812 bare this out. More men died of yellow fever than of any other cause. In war or peace, men still managed to contract illnesses.
Until the mid-19th century, the essential approach to such issues was one of “imbalance.” The humors, as originally specified by Galen in the first century CE, had to be in perfect order for the body to be healthy. Thus such treatments as bleeding and purging, incomprehensible to the modern mind, were commonly applied to draw out the ill-humors and right the body’s functions.
One of the most wince-worthy treatments of the time was blistering, which is not as often spoken of as bloodletting but was equally popular. This application was used to draw heat out of the body and was therefore applied in the case of fevers, swelling and sepsis. If an area of the body was red and hot to the touch, then it stood to reason – at least when applying the theory of humors – that the heat needed to be taken away with a form of like heat. Enter blistering.
Blistering agents, sometimes referred to as epispastics, were generally made of a wax or lard base. The key ingredient in almost all blistering plasters was cantharide beetles dried and then ground to a fine powder. The beetles, often called Spanish flies, had an irritant in their exoskeleton to discourage predators which would cause inflammation.
Along with use as a blistering agent, Spanish fly was also sprinkled on food or in wine as an aphrodisiac. The painful result, unfortunately, was an irritation of the urethra. Since this would sometimes lead to prolonged erections both in the male penis and the female clitoris, the use of Spanish fly has persisted into the modern era. (Don’t try that at home kids; you can end up needing to be catheterized in order to urinate. Nobody wants that.)
Mrs. Child, in her 1830s publication The Family Nurse, gives a straight forward recipe for a blistering ointment as well as instructions for application:
The common blistering plaster is made of fresh mutton tallow, yellow wax, resin of pine, cantharides, or Spanish flies; equal portions of each. The flies are finely powdered and added to the other ingredients previously melted together and removed from the fire. Usually spread on soft leather or kid, somewhat larger than the hand. If the surface be spread with powdered flies, it is more irritating. If this fails to draw a blister, Venice turpentine, powdered mustard and black pepper are sometimes mixed with it.
The optimal result saw large blisters breaking out on the “cherry red” skin. Mrs. Child goes on to up the teeth-gritting quotient by advising that, should the blisters formed by the plaster refuse to pop in a timely manner, they should be snipped “with sharp scissors” before linen is applied to absorb the desired discharge. She does mention that one should go light on the cantharides in plasters made for children.
The generally soft-hearted and homeopathic-leaning Mrs. Child also gives a number of ways to relieve the inevitable pain brought on by this treatment. These include cabbage or plantain leaves soaked in milk and used as a “soothing dressing.” It is doubtful that any navy surgeon would have troubled himself with such coddling of a patient; one shudders to think of the application of a blistering aboard a pirate vessel.
The distasteful regimen of blistering fell out of favor by the late 19th century, but a far less harmful remnant of the treatment remained. It is no doubt that most of our great-grandmothers applied a “mustard plaster” to their sick children. This smelly but harmless treatment was meant to clear up clogged nasal passages. A form of such home-brewed medicine remains today in the familiar application we know as Vicks Vapo Rub.
Header: Subtraction by H. Heath via Wikimedia (it will take more than a blistering plaster to help those sailors…)