The active ingredient in Sudafed is pseudoephedrine, which can increase blood pressure. People with high blood pressure (hypertension) should avoid pseudoephedrine. For people who do not have high blood pressure, the increase in blood pressure from taking pseudoephedrine is minor and temporary.

Keep in mind that pseudoephedrine is in many over-the-counter products for treating colds and allergy symptoms. People with high blood pressure must read product labels carefully to make sure they avoid "hidden" pseudoephedrine. Today, products that contain pseudoephedrine are stored behind pharmacists' counters.

If you have high blood pressure or heart disease, talk to your doctor before taking Sudafed or any product containing pseudoephedrine.