That funny taste you experience when drinking OJ after brushing is caused by sodium lauryl sulfate (also known as sodium laureth sulfate), an ingredient used in many personal care products, including toothpaste.

Sodium lauryl sulfate—an effective foamer—acts as a taste modifier, temporarily suppressing the sweet receptors of the tongue, says Dr. Marci Pelchat of the Monell Chemical Senses Center. Since sweetness blocks bitter and sour flavors, its absence enhances the bitterness and sourness found in the citric acid of orange juice.

A simple solution to this problem is to use sodium lauryl sulfate–free toothpaste. Or drink milk, which, because it isn’t sweet, seems less affected.

CHOW’s Nagging Question column appears every Friday.