The Food and Drug Administration is warning against using a controversial dietary supplement for the treatment of autism.

In a letter to the makers of a drug known as OSR#1, federal officials say the product is toxic and is not labeled to inform users of possible side effects like problems with the pancreas and hair loss.

OSR#1 originated as an industrial compound to treat wastewater in mines, but it is currently sold in pill form and some parents believe it helps mitigate symptoms of autism.

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Because OSR#1 is marketed as a dietary supplement it has not been required to undergo the intense scientific scrutiny that’s required of traditional drugs. However, the FDA is taking notice, saying in their letter that OSR#1 does not qualify as a dietary supplement and must be reviewed like any other new drug.

The company selling OSR#1 has 15 days to respond to the FDA letter, reports The Chicago Tribune. To read more click here.