Why is Epinephrine used during an allergic reaction?

As a person with environmental allergies, I am no stranger to the symptoms of an allergic reaction. Itchy red eyes, a sore throat and uncontrollable sneezing? We’re all best friends.However, unlike my food-and-insect-allergic counterparts, I have only experienced anaphylactic reactions — allergic reactions that can result in the inability to breathe — twice; once after being administered allergy shots that contained a particularly high dose of allergens, and the second during a failed interaction with an avocado.

During my first reaction, I was in a doctor’s office and was given a shot of epinephrine to help me breathe. But the second reaction happened while I was at home attempting to cook. Although the reaction was slight, it happened while eating an avocado, a food I had previously been tolerant of. So my doctor prescribed me an EpiPen, in case of emergencies.

An EpiPen is a tubular, hand-held injection device (roughly the size of a tube of toothpaste) filled with the hormone epinephrine. When you correctly administer an EpiPen, you actually inject a small dose of epinephrine into the bloodstream by forcibly releasing the hormone through a needle into your upper thigh. When you press the tip of the EpiPen against your thigh to release the medication inside, it makes a clicking noise, like pressing the top of a retractable pen. The tip of this pen just happens to have a needle in it.

Epinephrine, more commonly referred to as adrenaline, is a naturally occurring substance within the body. Most people think of adrenaline when they hear “fight or flight.” That’s because epinephrine is extremely important in the contraction and relaxation of muscles, in a person’s feelings of energy, fear, and awareness, and even to the metabolism of sugar in the bloodstream. Epinephrine is produced in the medulla, or middle, of the adrenal glands, which sit on top of the kidneys and are key producers of hormones for the body.

Some epinephrine receptors, specific surface proteins that receive signals from epinephrine, also control smooth muscle cells. Smooth muscle cells comprise the organs in our bodies that perform automatic functions you don’t consciously think about using, like your veins or your stomach. Smooth muscle, aptly named for its non-grooved surfaces, cannot be broken down and built back up like the skeletal muscle in our arms and legs.

Epinephrine is used, be it for both allergic reactions and heart attacks, in an effort to increase blood flow through veins and to reduce swelling in airways. When epinephrine is recognized by receptors on smooth muscles, it causes airway-blocking muscle constriction to subside. A dose of epinephrine signals for your veins to constrict, to pump more blood, and for your muscles to relax, so breathing and blood flow return to normal.

However, epinephrine is only a temporary treatment for allergic reactions, not a solution (unlike an antihistamine, which is more commonly used to treat allergic symptoms like hives and hay fever.) This means that those who have used an EpiPen should seek immediate medical attention to ensure that the reaction is completely diminished.