Monday Pharmaceutical Mystery: What Caused Health-conscious People to Get Incredibly Sick in 1989?


In 1989, more than 1500 young, healthy people started experiencing mysterious symptoms that included unusual skin rashes, muscle pains, dramatic eosinophilia, and tightening of the skin.

In 1989, more than 1500 young, healthy people started experiencing mysterious symptoms that included unusual skin rashes, muscle pains, and dramatic eosinophilia, as well as a tightening of the skin that resembled scleroderma.

Many of these people were health-conscious individuals who ate healthy foods and took natural supplements and vitamins for better energy, mood, and sleep.

Over time, the mysterious symptoms of these patients grew worse. One patient, a concert pianist, lost her ability to play the piano. Other patients lost the ability to walk and live normal lives. Many were declared disabled. In total, 38 people died from these mysterious symptoms.

Medical experts at the CDC, National Institutes of Health, FDA, and Mayo Clinic, as well as other physicians around the country, were called in to solve this mysterious epidemic. The only solid piece of information that they had to consider was that all of the people affected had high eosinophil counts, which are the white blood cells associated with allergens and parasitic infections. However, the patients had no apparent presence of parasitic infection.

Mystery: What caused these health-conscious individuals to get incredibly sick in 1989?

Solution: A physician in New Mexico linked the epidemic to a contaminant in a common natural supplement all of the patients were taking. This contaminant was in all of the L-tryptophan pills being produced at the time, regardless of the manufacturer.

The contaminant was found to be introduced to the supplement early in the manufacturing process before they were shipped to the United States. Upon arriving in the country, the contaminated raw materials were distributed through various manufacturers and distributors.

L-tryptophan is an amino acid and precursor to serotonin and melatonin. People use L-tryptophan for improved mood, sleep, energy levels, and overall good health.

Upon discovery of this contaminant present in the supplement, the official diagnosis for patients with these symptoms was eosinophilia-myalgia syndrome.

Today, L-tryptophan is more thoroughly regulated by the FDA and MedWatch than other natural products. Both organizations now have a reporting system for adverse events, and they take swift action to disseminate important information about supplements to the public and take corrective action as needed.


Centers for Disease Control and Prevention. “We were there” — Toxic Oil. CDC website. Page updated March 20, 2020. Accessed September 28, 2020.

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