taken from
http://www.quackwatch.org/02ConsumerProtection/FDAActions/bachynsky.html:
In the July 15, 1933, issue of the Journal of the American Medical Association (JAMA), three Stanford University researchers reported that patients receiving daily oral doses of 3 to 5 milligrams of dinitrophenol per kilogram of body weight experienced steady weight reduction without demonstrable side effects.
In the Sept. 30, 1933, issue of JAMA, three San Francisco physicians described a severe skin reaction in a woman who had taken dinitrophenol for 14 days.
in 1934 an estimated 100,000 persons took the drug for weight reduction. More than 1,200,000 capsules were dispensed from a single clinic in San Francisco.
In April 1935, a virtual epidemic of cataracts began to occur, predominantly in young women who had been taking dinitrophenol. Some cases showed up months or years after the last dose of the drug had been taken. Tragically, once started, changes in the eye's lens progressed rapidly until vision was obscured. Dr. Warren D. Homer, a San Francisco ophthalmologist and one of the first to report dinitrophenol-related cataracts, estimated that more than 164 people were affected.
In 1938, the Federal Food, Drug, and Cosmetic Act was enacted, giving FDA the power to take action against drugs that are dangerous even when used in the recommended dosage. Subsequently, the agency included dinitrophenol in a list of drugs potentially so toxic that they should not be used even under a physician's supervision.
[...]
The doctor, Nicholas Bachynsky, operates a chain of "Physicians Clinics" throughout Texas and in several other states. Until last December the mainstay of his weight-loss program in Texas was dinitrophenol, which he dispensed under the trade name Mitcal. According to his advertising brochures, Russian-born Bachynsky learned of dinitrophenol in 1963 while translating Russian medical journals for the U.S. government. The Russians used it to keep soldiers warm in winter, he learned. The main side effect reported was weight loss.
Although Bachynsky's brochure stated, "There have been no fatalities associated with Mitcal," the consent form patients were asked to sign lists among the potential risks of his treatment "blood clots in veins and lungs; cataract formation; hemorrhage; allergic reactions; and even death." This apparently wasn't enough to dissuade prospective patients. As many as 14,000 people were treated at Bachynsky's clinics, according to court papers.
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out of more than 100000 users, ~150 developed cataracts and we don't know what these people were also using back in the 1930s. this calling an "epidemic" is grossly overblown. the FDA wanted more powers and they used DNP as one of many tools for getting it.
14000 users in 1984 and not a single fatality, only "sides" reported were fever, shortness of breath, dizziness and sweating. duh, thats what DNP is supposed to do.
allergies were never cited as an adverse reaction, maybe allergies in general are a quite new thing not widely known in the 30s, but thats the only thing i would look out for. otherwise i will continue to use DNP without thinking twice.