If you have high blood pressure, you need to be cautious when taking over-the-counter (OTC) medicines for coughs, colds, and flu. Most people didn’t know they were at risk if they took certain decongestants, according to a survey by St. Joseph Health Products.

Here’s the caution: The most common OTC ingredient to avoid: decongestants. OTC cough and cold medicines with decongestants help to reduce nasal swelling in part by narrowing the blood vessels in the nose and facial area. However, the narrowing effect of decongestants can also affect other blood vessels while increasing blood pressure and heart rate, making it a potentially dangerous situation for the millions of Americans who have high blood pressure.

Talk with your doctor or pharmacist about which cold and cough medications might be better for you if you have high blood pressure.