NASCAR has suspended driver Jeremy Mayfield for violating its substance abuse policy. ESPN’s Ed Hinton reports that “sources close to the situation said Mayfield claims he took Claritin D, an over-the-counter allergy drug that contains pseudoephedrine, a substance banned by most sports.” NASCAR does not have a list of banned substances. It punishes what it calls the abuse of any drug.

If you are a normal person who does not have to worry about the police finding your Riverside, Calif., meth lab, there is no reason for you to be aware of the side effects of pseudoephedrine. I do not know whether or not Mayfield took pseudoephedrine, but here’s why an athlete might.

First off, pseudoephedrine is legal. (Claritin, after all, is a NASCAR sponsor.) The drug relieves nasal or sinus congestion caused by the common cold, sinusitis, hay fever and other respiratory allergies. It temporarily relieves sinus congestion and pressure by causing a narrowing of the blood vessels in the nasal passages.

According to The National Institutes of Health, over-the-counter stimulants containing ephedrine or its related alkaloids also can be used to enhance athletic performance. Stimulants increase energy, alertness and aggressiveness and reduce appetite and fatigue. Products containing ephedra alone, or combined with vitamins, minerals and other botanicals, are marketed to increase energy and enhance athletic performance. Baseball players have a long relationship with stimulants.

Why shouldn’t an athlete use them? Stimulants have a number of negative side effects, including heart failure.