Does Benadryl Raise Blood Pressure?

Benadryl is a widely used over-the-counter medication known for its antihistamine properties. Its active ingredient, diphenhydramine, helps to alleviate allergy symptoms by blocking histamine in the body. Although it's a popular choice for allergy relief, concerns have been raised regarding its potential impact on blood pressure.

Allergies and Benadryl -- Hypertension?

The relationship between Benadryl and blood pressure is complex. While some studies have found a link between the use of Benadryl and elevated blood pressure, the extent of this relationship can vary depending on individual health conditions, dosage, and frequency of use. Additionally, Benadryl can interact with other medications, further influencing its impact on blood pressure.

There may be concerns about the potential effects of Benadryl on blood pressure. This is mainly due to two reasons:

Anticholinergic effects

Acetylcholine is a neurotransmitter, a type of chemical messenger that transmits signals across a chemical synapse, such as a neuromuscular junction, from one neuron (nerve cell) to another "target" neuron, muscle cell, or gland cell. It plays a significant role in the autonomic nervous system, which is the part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, heartbeat, and digestive processes.

One of the primary functions of acetylcholine is to help regulate heart rate and the dilation of blood vessels. When acetylcholine binds to receptors on the heart, it can slow the heart rate down. Similarly, when it binds to receptors on blood vessels, it can cause them to dilate (widen), which can lower blood pressure.

      Anticholinergic drugs, like diphenhydramine, work by blocking the receptors that acetylcholine binds to, thus inhibiting its action. This can result in a range of effects, including an increase in heart rate (since the heart-rate-slowing effect of acetylcholine is blocked) and a decrease in the diameter of blood vessels (since the blood-vessel-widening effect of acetylcholine is blocked).

          Both of these changes—increased heart rate and decreased diameter of blood vessels—can potentially lead to an increase in blood pressure. This is because blood pressure is a measure of the force of blood pushing against the walls of the arteries as the heart pumps blood, and it is determined by the amount of blood your heart pumps and the amount of resistance to blood flow in your arteries. Thus, if more blood is pumped (due to an increased heart rate) and the arteries are narrower (due to decreased blood vessel diameter), blood pressure can increase.

              That being said, in most healthy individuals, the occasional use of diphenhydramine is unlikely to cause significant increases in blood pressure. However, chronic use or use in individuals with already high blood pressure could potentially exacerbate the condition. As always, it's important to use medications as directed and discuss any concerns with a healthcare professional.

              Sedative effects

              Diphenhydramine is categorized as a sedating or first-generation antihistamine. These types of antihistamines easily cross the blood-brain barrier, a protective layer of cells that regulates what substances enter the brain from the bloodstream. Once in the brain, diphenhydramine can block histamine activity, which leads to a decrease in the symptoms of allergies. However, this also tends to cause sedation or drowsiness, a common side effect of first-generation antihistamines.

              Now, in terms of blood pressure, the relationship between sedation and blood pressure isn't as direct. The sedative effects of diphenhydramine could lead to decreased physical activity, and a lack of physical activity is a known risk factor for high blood pressure over time. Regular physical activity makes your heart stronger, and a stronger heart can pump more blood with less effort. If your heart can work less to pump, the force on your arteries decreases, reducing your blood pressure. Therefore, anything that leads to decreased physical activity, such as the sedative effects of a medication like diphenhydramine, could potentially contribute to higher blood pressure over time.

              However, this would likely only be a concern with chronic, long-term use of the medication, and even then, it would just be one factor among many that could contribute to high blood pressure. Factors such as diet, overall physical activity levels, stress, and genetic factors also play a significant role in determining an individual's blood pressure. As always, it's important to use medications as directed and discuss any concerns with a healthcare professional


              If you have high blood pressure, it's important to explore alternatives to Benadryl. Safer antihistamine options, such as loratadine or fexofenadine, may be more appropriate for those with hypertension. Non-pharmacological allergy relief methods, like nasal irrigation or using air purifiers, can also help alleviate symptoms without affecting blood pressure. Always consult your healthcare professional before starting any new medication.

              Wrap Up

              Monitoring your blood pressure while taking Benadryl is crucial. Regular blood pressure checks, using tools like home blood pressure monitors or smartphone apps, can help you track any changes. If you notice a significant increase in blood pressure or experience symptoms such as dizziness or headaches, it's essential to seek medical advice.

              Managing high blood pressure and allergies simultaneously can be challenging but is possible with the right approach. Adopting a balanced diet, engaging in regular physical activity, and implementing allergy prevention strategies can help you achieve better control over both conditions.