1. Benzoic acid: It's a compound used as a food preservative. In three different experiments, he inhaled vapors and fumes of the substance, and applied a solution of it to the mucous membranes inside his nose. His conclusion was that the substance did not cause hay fever symptoms. (2, pages 51-53) (5, page 71-73)
2. Coumarin: A chemical compound found naturally in some plants, and can be used as a food additive or in some perfumes. He placed ten drops of the substance upon a plate, thus allowing it to evaporate into the air of the room. He and a couple friends entered the room, spending a couple hours at a time on more than one occasion. The men walked around the room as to inhale the air as if they were walking in the open air. He even performed this experiment in different years and during different seasons of the year. The experiments did not produce hay fever symptoms. (2, pages 53-55) (5, pages 73-75)
3. Odours: He inhaled the odours of various plants, flowers, fungi and other substances. Some produced hay symptoms and some others didn't. The substance that came closest to producing hay fever symptoms was Penicillium. His recommendation was for further testing in this area. (2, pages 55-59) (5, pages 76-79)
4. Ozone: It was discovered in 1785 by Dutch physicist Martinus Van Marum (1750-1837), and is a naturally occurring substance created by the sun. Christian Friedrich Schonbein described in 1832 how it can be produced by man. Dr. Schonbein said he observed catarrhal affections such as asthma and hay fever among those who, during experiments he performed, inhaled air highly charged with it.
During the 1850s various other physicians made similar observations, and so did Dr. Phillip Phoebus in 1862. Blackley set out to prove if this was true. In some experiments he spent several hours, at various seasons of the year, in locations with high levels of measurable ozone in the atmosphere, and he observed no hay fever symptoms. He also artificially created an atmosphere high in ozone in a room, and he spend six hours in it while experiencing no ill effects.
He also observed that ozone was always present, even in the atmosphere on the seashore and out at sea, where many hay fever sufferers have reported relief of symptoms. He therefore concluded that if ozone caused hay fever, symptoms would be observed in these locations.
In this way he was able to disprove the theory that ozone caused hay fever symptoms. (2, pages 59-69) (2, page 8, pages 79-91)
5. Dust: Blackley said many authors referred to dust as "common dust," and he said there is no such thing, as all dust contains different ingredients depending on the geological character of the district and its botanical productions. He said various germs may also appear in the dust depending on temperature and moisture of the air.
He said dust produces hay fever symptoms, but only during the hay or flowering season. He did observe that symptoms occurred when a horse and buggy stirred up dust, but he attributed this pollen carried carried by the horse and buggy and not the dust.
In other words, he attributed symptoms caused by dust not so much on the dust, but on pollen mixed with the dust. He said he would further prove this by performing experiments with pollen. (2, pages 69-72) (5, pages 90-93)
6. Pollen: He performed five different types of experiments with various types of fresh and dry grass and flowering pollens: he applied them to the mucous membrane inside a patient's nose, he had the patient inhale them to bring them into contact with the throat and lungs, he applied them to eyelids and lips, and he rubbed them on limbs. (2, page 76)
Upon completion of his experiment on pollen, he said:
Almost every experiment (with pollen) is by a greater or smaller amount of definite and unmistakable effect which seems to point to pollen as the most powerful if not the only cause of the malady. (2, page 74)In this way, he proved that, without a doubt, pollen was the main cause of hay fever, both in its catarrhal and asthmatic forms. He also determined that even a small amount of pollen may cause these symptoms, although the severity depended on the type and the quantity of pollen. (2, page ?, 99)
7. Animals: Various physicians had noted that some animals, such as cats, rabbits and guinae pigs, brought about hay fever symptoms. Blackley suspected that this was due to pollen being carried withing the fur of these animals. (2, pages 101-102)
8. Light: Regarding this, he said:
We have abundant evidence to show the important influence it has in aiding those changes that make up the sum total of life in the animal and vegetable kingdom, but we have no evidence to show that it has the power to produce symptoms which have even a remote resemblance to those of hay fever, and, so, as far as I am aware, no author has yet made experiments which prove that light can produce the fully developed disease." (2, page 102)He said that until evidence shows otherwise, he cannot accept that light is the cause of hay fever. (2, page 102-103)
9. Heat: Many credible physicians, including Dr. Bostock, postulated this to be the cause. However, if this were true, hay fever sufferers would not get a reprieve while visiting the city or the sea side, as the weather would be the same at these locations as anywhere else. He said the disease would equally appear in southern states as northern states, and in fact Dr. Morrill Wyman proved there are fewer cases of hay fever in the south.
Blackley essentially said John Bostock's experiments that showed hay fever was caused by heat were flawed. Blackley said:
I have... shown that in a cool summer very little pollen is formed by grass, and I shall be able to show... that a rise in the temperature, during the hay season, will sometimes cause large quantities of pollen to be formed and thrown off... certain it is that heat and moisture favor the growth and evolution of pollen and that cold and dryness will almost completely put a stop to these processes. (2, page 104-105)Lacking this knowledge, it must have been easy for wise physicians like John Bostock to assume that heat was the cause of the symptoms, instead of just a contributing factor.
- "Charles Harrison Blackley, 1820-1900," The University of Manchester: The John Ryland University Library: Manchester Medical Collection, http://archives.li.man.ac.uk/ead/search?operation=full&rsid=dc.title%20any%2Frelevant%2Fproxinfo%20%22William%20Charles%20Henry%22&firstrec=1621&numreq=20&highlight=1&hitposition=1638, accessed 9/13/14
- Blackley, Charles Harrison, "Experimental Researches on the Causes and Nature," 1873, London, Bailliere, Tindall, and Cox
- Waite, K.J., "Blackley and the development of hay fever as a disease of civilization in the nineteenth century," Medical History, April, 1995, 39 (2), pages 186-196, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1036974/?page=5, accessed 9/14/14
- Smith, William Abbotts, "On Hay-Fever, Hay-Asthma, or Summer Catarrh," 1867, London, Henry Renshaw, pages 17-24.
- Blackley, Charles Harrison, "Hay Fever: It's causes, treatment and effective prevention," 2nd edition, 1880, London, Bailliere, Tindall, & Cox