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Nothing to Sneeze At
EMS providers frequently encounter patients experiencing allergic reactions. These can result from a variety of factors and produce various signs and symptoms, from a runny nose to cardiac arrest. Understanding the processes of these reactions, how they present and how to treat them is important.
First and foremost, the safety of the provider is paramount. Many things that cause allergic reactions can also be harmful to responders, especially insects. Wear disposable gloves, as well as a gown and/or mask with eye protection, as the situation requires.
What Is an Allergic Reaction?
An allergic reaction is an attempt by the body to neutralize or rid itself of a foreign substance (antigen). Most antigens are fought off by the body's immune system, and most of the time, humans are unaware this process is even taking place. Antigens can enter the body in four ways: injection, inhalation, ingestion and absorption. Just as with medication, some pathways work faster than others.
Usually, people don't have allergic reactions the first time they're exposed to an antigen. The body initially forms a protein and releases it into the bloodstream to fight the antigen. This is known as an antibody. Each antibody is created to combat a specific antigen to which the body's been exposed. After that initial exposure and production of antibodies, the body is susceptible to an allergic response the next time it encounters the antigen, be it days, weeks, months or even years later.
After subsequent exposures to the antigen, antibodies combine with the antigen to produce the allergic response. The antigen has then become an allergen—something that triggers an allergic reaction. Most allergic reactions are relatively mild, such as watery eyes, runny nose and skin irritation (itching and redness), and are remedied through over-the-counter medications such as antihistamines. However, some reactions can be severe, potentially involving many different body systems. These severe reactions are referred to as anaphylaxis. In anaphylaxis, exposure to the allergen causes blood vessels to dilate and a decrease in blood pressure. It also causes swelling of respiratory tissues, which causes airway constriction and the possibility of complete obstruction. Anaphylaxis is a life-threatening condition that must be treated quickly.
Routes of Exposure
There are several ways allergens can be introduced into the body. Routes of exposure can be vital to understanding causes and best treatments.
Injection, such as from an insect bite or sting, is the most common and rapid-acting route of exposure, as it often introduces the allergen directly into the bloodstream. Symptoms usually occur within minutes. Injection exposure can also come from needles and even administration of medications to which patients are allergic.
Ingestion is also common, and incorporates both food and many drug allergies. Food allergies are believed to be the leading cause of anaphylaxis outside the hospital setting, causing an estimated 30,000 emergency department visits and 150–200 deaths in the U.S. each year.1 Any food can cause a severe reaction in someone who's allergic to it. Nuts, shellfish, fish, milk and eggs are common causes of food-induced anaphylaxis. Very small amounts are all that is needed to cause a reaction in some people. People allergic to foods usually avoid them, but may ingest them unknowingly.
Allergic reactions to medications are also common, and it is estimated that up to 1% of the population may be at risk for them.1 Due to the slow absorption of medications in the GI tract, it may be some time after ingestion before a reaction occurs. Medications that commonly cause allergic reactions include antibiotics, local anesthetics and vitamins.
Inhalation allergies are commonly associated with environmental allergens such as animal dander, dust and molds, and pollen from weeds, plants and grasses. Smoke from burning plants can also cause allergic reactions.
Absorption or contact allergies are typically less severe but last longer, mostly due to localized irritation. Contact with some types of plants (e.g., poison ivy, oak and sumac) will cause allergic reactions. People have also experienced allergy symptoms when exposed to soaps, perfumes, detergents, makeup, lotions, glues and other chemicals.
Over the past few years, latex allergies have become especially prevalent. It is estimated that 8%–12% of all healthcare workers have latex sensitivity. Between 1988–92, the FDA received more than 1,000 reports of adverse health effects from exposure to latex, including 15 deaths.2 Most EMS agencies now provide latex-free gloves and equipment.
Allergic reactions can affect all the main body systems. Recognizing the signs and symptoms expediently can make the difference in the severity of the reaction and the patient's condition overall. Table 1 on the previous page outlines the systems commonly affected by allergic reactions, with their associated signs and symptoms.
Identifying the Culprit
Clues on scene may suggest a type of exposure. If you're called to a restaurant, be suspicious of a food reaction. At an outdoor scene, it may be a bite or a sting. A call to a medical facility may stem from a medication reaction. Additionally, be sure to include questions that relate to the condition:
- Has the source of the allergic reaction been found (especially in situations where the scene may not be safe)?
- Has the patient ever reacted like this before?
- When did the symptoms onset?
- Does the patient have a past history of allergic reactions? If so, to what?
- Does the patient have an epinephrine auto-injector?
Assessment and Treatment
Like with many medical emergencies, the EMT must pay special attention to the ABCs in patients experiencing allergic reactions. Securing and maintaining an airway is important, but may be difficult with occlusion due to swelling. Auscultation may show wheezes or other signs of respiratory distress. Check pulses, skin temperature and color, and capillary refill for signs of decreased circulation or hypoperfusion. Based on the type of exposure, conduct a quick inspection of body surfaces for bites, stings or injection sites, as well as general redness and swelling. Note that symptoms may worsen very quickly, and victims should be rapidly transported to definitive care.
Provide oxygen via nasal cannula for mild symptoms, and non-rebreather or even bag-valve ventilations for moderate to severe symptoms. Consider the use of oral or nasal airways to assist in keeping the airway open, or advanced airway devices if your protocols allow.
The other intervention used by EMTs to treat allergic reactions is epinephrine. Epinephrine (also called adrenaline) is a hormone secreted by the body in response to a physical or mental stress, and initiates many of the body's responses to fear or injury. In anaphylaxis, it dilates airways (bronchodilation) and constricts blood vessels (vasoconstriction). Vasoconstriction increases blood pressure and heart rate.
Epi is commonly administered by EMT-level providers via an auto-injector. An auto-injector has a spring-loaded needle that injects the medication when the spring is triggered, usually against the skin. There are no contraindications to administering epi in a life-threatening situation, though doing so may cause side effects, including tachycardia, dizziness, chest pain, anxiety, headache, nausea and vomiting.
Prior to administering the auto-injector, the EMT should assist the patient to a sitting or supine position. If the patient is in shock, elevate their feet. Assess vital signs every five minutes. If the patient has their own auto-injector, assist them in using it. If the patient's auto-injector is not available or has expired, and the EMS agency is authorized to carry an auto-injector, use that. If the patient has not been prescribed an auto-injector, contact medical control for authorization.
To use the auto-injector, first check the medication inside. It should be clear and colorless; if it's not, don't use it. Remove the safety cap, but don't put fingers over the tip when doing so, or after the cap has been removed.
Typically, the injection site is the thigh. Cleanse an area halfway between the patient's waist and knee with alcohol prior to injection. Place the auto-injector tip over the site. It is possible to inject through clothing, but bare skin is recommended. With a rapid motion, push the auto-injector firmly against the thigh to activate the injector. Hold it in place for 10 seconds. Some models have a window on the pen that will change color after the medication is injected. Dispose of the auto-injector immediately in a biohazard sharps container. Record the time of the injection and document any patient reaction.
After administration, reassess the patient's vital signs, especially respiratory status. If you're not already en route to the hospital, get going. If additional doses are needed, contact medical control. If the patient's condition deteriorates, treat appropriately. If the patient goes into cardiac arrest, perform CPR per accepted guidelines. If the patient improves, continue to administer oxygen and monitor for changes.
References
Timothy J. Perkins, BS, EMT-P, is the EMS systems planner for the Virginia Department of Health's Office of EMS. He has over 17 years of EMS operations and management experience. E-mail him at tjperkins5@yahoo.com.
