Vicks VapoRub (also commonly called vapor rub, vaporizer, inhaler) — one of the most trusted over-the-counter remedies against cough and cold here in the Philippines may cause airway inflammation that can restrict breathing in infants under age two.

Dr. Bruce Rubin of Wake Forest University School of Medicine in North Carolina said the ingredients in Vicks can be irritants, causing the body to produce more mucus to protect the airway. And since infants and young children have airways that are much narrower than those of an adult, any increase in mucus or swelling can narrow them severely.

“The company [Procter & Gamble Co] is really clear it should never go under the nose or in the nose for anybody and it shouldn’t be used in children under 2,” said Rubin, whose study appears in the journal Chest.

While the researchers only tested the Vicks product, Rubin said similar products, including generic versions, could cause the same negative effects in infants and toddlers.