Blood pressure naturally fluctuates each day according to the body's circadian rhythms, reports the Los Angeles Times. For most people, this means their blood pressure is low in the mornings and highest in the middle of the afternoon. Hypertension, stress, strong emotions and food sensitivities can also cause daily blood pressure fluctuations.
People with high blood pressure that was uncontrolled for several years often have blood vessels that tighten easily, notes the Los Angeles Times. Therefore, hypertension itself can cause widely variable blood pressure readings throughout the day.
Food allergies can also trigger high blood pressure, so people who have high blood pressure may want to consider trying an elimination diet, explains Psychology Today. Someone who is sensitive to salt, for example, could trigger a blood pressure spike by eating salty food, states the Los Angeles Times.
People with anxiety may also experience sharply elevated blood pressure during an anxiety episode, according to Mayo Clinic. Even though these spikes do not last long, if they occur regularly, they can damage the heart, blood vessels and kidneys.
Identifying the root cause of blood pressure variations is important because research suggests that these fluctuations increase the risk of a stroke in postmenopausal women, notes Columbia University College of Physicians and Surgeons. The risk of stroke from these fluctuations disproportionately affects women with normal blood pressure rather than women with hypertension.