Phenylpropanolamine hydrochloride (PPA), a substance found in over-the-counter weight loss products, cold medicines and sinus remedies, has long been associated with adverse reactions ranging from severe headaches to fatal strokes. Although the effects of PPA have prompted more than a dozen lawsuits, this investigation revelas that manufacturers continue to insist that products containing the chemical are safe, and government officials have yet to complete their review of it.