Food allergies can cause an increased heart rate, known as tachycardia, as part of a larger systemic response. A food allergy is an immune system overreaction to a typically harmless protein found in food. When a sensitive individual consumes an allergen, the body mounts a defense that rapidly affects multiple organ systems, including the cardiovascular system. The increased heart rate is a direct physiological consequence of the body attempting to manage this widespread immune response.
The Allergic Cascade and Cardiovascular Response
The process begins when mast cells, immune cells abundant throughout the body, are activated by the food allergen. Once triggered, these cells rapidly release chemical mediators, including histamine and other inflammatory molecules. Histamine is a potent signaling molecule that immediately affects the circulatory system.
Histamine release causes widespread vasodilation, the widening of blood vessels throughout the body. This vasodilation, combined with increased capillary permeability, causes fluid to rapidly leak out of the blood vessels and into surrounding tissues. This sudden shift of fluid out of the circulation causes a dramatic drop in blood pressure, a condition called hypotension.
The heart responds to this sudden drop in blood pressure and reduced circulating volume by accelerating its pace. This rapid beating, or compensatory tachycardia, is the heart’s immediate attempt to pump faster to maintain blood flow and oxygen delivery to vital organs. Without this compensatory mechanism, the body would quickly enter a state of shock due to insufficient blood perfusion.
Tachycardia as a Marker of Systemic Severity
An increased heart rate is a serious indicator of the severity of the allergic reaction, particularly signaling the onset of anaphylaxis. Anaphylaxis is a severe, systemic, and life-threatening reaction that affects breathing or circulation. While skin and respiratory symptoms are often noticeable, cardiovascular symptoms frequently dictate the overall outcome.
In mild, localized allergic reactions, such as minor hives or tingling in the mouth, the heart rate typically remains normal or minimally affected. However, a pronounced or rapidly developing tachycardia suggests that the inflammatory chemicals have spread systemically, affecting the body’s central circulatory control. Tachycardia is observed in about a quarter of patients experiencing anaphylaxis and is a classic sign of the body’s attempt to counteract severe hypotension.
A fast heart rate is often accompanied by other signs of circulatory distress, such as dizziness or feeling faint. The drop in blood pressure may cause the individual to feel a sense of impending doom, a recognized symptom of severe systemic reactions. Rapid onset tachycardia combined with low blood pressure indicates the body is struggling to maintain adequate perfusion, which can precede cardiovascular collapse if not treated quickly.
Immediate Action and Emergency Protocol
If a rapid heart rate occurs alongside other signs of a systemic reaction, such as difficulty breathing or swelling of the throat, immediate action is necessary. The most important step is the immediate administration of an epinephrine auto-injector, if one is available. Epinephrine works rapidly to reverse anaphylaxis by constricting blood vessels to raise blood pressure and relaxing airway muscles to improve breathing.
Following the use of epinephrine, emergency medical services must be called immediately by dialing 911 or the local equivalent. Even if the symptoms appear to improve after the injection, the person still needs to be transported to a hospital for observation and follow-up care. The effects of epinephrine may wear off, and a second, or biphasic, reaction can occur hours later.
While awaiting emergency personnel, the person should lie flat with their legs elevated to help increase blood flow to vital organs. If the individual is vomiting or has significant breathing difficulty, they should be turned onto their side or allowed to sit up. Note the time the epinephrine was given, as a second dose may be required after five to fifteen minutes if symptoms have not improved or have worsened.