Allergy & Anaphylaxis
By Kenneth L. Reed, DMD
Of all medical emergencies that can and do occur in dental offices, allergy-related emergencies are actually quite common. As a matter of fact, based on data from Malamed, a “mild allergic reaction” was the second most common medical emergency seen in dental offices behind only syncope (fainting).1 Additionally, “anaphylaxis” was the 11th most common medical emergency seen in dental offices. The most common allergen in the dental environment today, of course, is latex.2 Penicillin is the most common cause of drug-induced anaphylaxis.3 Patients will always have allergies to penicillin and the penicillin-like drugs (amoxicillin, Augmentin®, etc) and other drugs and agents prescribed, administered and dispensed in dental offices. It should be noted here that a true allergic reaction to an injected local anesthetic in dentistry has an incidence that approaches zero. It simply does not occur to any measurable degree.4
If the allergic reaction presents as itching, hives, or a rash as the only signs and symptoms, the allergy may be considered mild (non-life–threatening). However, if the patient experiences cardiovascular and/or respiratory embarrassment, which are normally seen as dizziness or loss of consciousness due to an inadequate blood pressure and/or inadequate blood flow to the brain (cardiovascular issues), or difficulty in breathing (respiratory issues), the dental professional must treat the allergy as a life-threatening situation.5
Allergic reactions occurring many minutes to m any hours after exposure to the allergen may be termed “delayed onset” while those that occur within a few seconds to a few minutes after contact with the allergen are termed “immediate onset.” As a general rule, the faster the signs and/or symptoms occur, the more severe the allergy typically will be.
If the allergy is mild (that is, itching, hives, and/or rash only) and the patient remains conscious, he or she should be made comfortable. There are two main positions that we may choose to place patients in as they are experiencing a medical emergency. If the patient remains conscious, we want to make them comfortable. These patients may wish to sit upright or be reclined. Either is acceptable. If the patient loses consciousness, the patient is placed supine (flat). Almost all medical emergencies where loss of consciousness occurs share the same cause, low blood pressure in the brain. Making the patient supine will increase blood pressure in the brain and allow the patient to regain consciousness in most cases.
Also, the conscious patient who is talking has verified that their airway is patent, he or she is breathing, and cardiovascular function is adequate to maintain consciousness. We have just verified the A–B–C steps of CPR. Even though the new CPR guidelines call for C–A–B, for medical emergencies occurring in dental offices, A–B–C is still appropriate.
Treatment for a mild allergic reaction involves the administration of a histamine blocker, such as diphenhydramine, via intramuscular or intravenous injection. The adult patient should be administered 50 mg, and the child patient should receive 25 mg. Oxygen is never wrong, but often is not required in cases such as these. Oral administration of diphenhydramine may have too long an onset of action to be of any practical use during this type of medical emergency so parenteral administration of the diphenhydramine is preferred. Patients administered parenteral diphenhydramine should also be prescribed oral diphenhydramine for a period of 3 days; 50 mg four times daily for an adult and 25 mg four times daily for a child. Histamine and other substances that contribute to allergy may circulate in the bloodstream for 3 days after the initial insult, so it is important to have the patient prophylactically covered during this time.
Severe Allergy (Anaphylaxis)
Anaphylaxis is an acute life-threatening systemic reaction with varied mechanisms and clinical presentations.3 Immediate discontinuation of the offending drug(s) and early administration of epinephrine are the cornerstones of treatment. Epinephrine is the drug of choice in the treatment of anaphylaxis, because its alpha-1 effects help to support the blood pressure while its beta-2 effects provide bronchial smooth-muscle relaxation.6 Absorption is more rapid and plasma levels are higher in patients who receive epinephrine intramuscularly in the thigh with an autoinjector.7 Intramuscular injection into the thigh is also superior to intramuscular or subcutaneous injection into the arm.8 No established dosage or regimen for intravenous epinephrine in anaphylaxis is recognized. Because of the risk for potentially lethal arrhythmias, epinephrine should be administered intravenously only during cardiac arrest or to profoundly hypotensive subjects who have failed to respond to intravenous volume replacement and several injected doses of epinephrine.3
If the allergy is severe, the patient has lost, or soon will lose, consciousness. The dentist should place the patient in a supine position, open the airway, and evaluate breathing. Often, breathing is spontaneous and adequate. If the patient is not breathing, the dental professional must administer positive pressure oxygen via a bag–valve–mask device. If the patient has lost consciousness, his or her cerebral blood pressure is too low. Another dental staff also must contact EMS (generally 911) as the patient requires additional treatment in the hospital’s emergency department. The appropriate pharmacologic management for anaphylaxis in an outpatient setting is outlined in Table 1.
Several options exist for treating patients who may have a history of allergic reactions. First is consultation with an allergist to test the patient for allergy to the drug in question. Treatment should be postponed if at all possible until this can be accomplished. Next is the use of general anesthesia if the allergy was to a local anesthetic. Although general anesthesia is highly useful, it is not available in most dental offices. Another option if the allergy was to a local anesthetic is the use of a histamine blocker, such as diphenhydramine, as a local anesthetic for pain management during treatment. Most injectable histamine blockers possess local anesthetic properties. Diphenhydramine has been the most commonly used histamine-blocker in this regard.4
1. Malamed SF. Managing medical emergencies. J Am Dent Assoc. 1993;124(8):40-53.
2. Desai SV. Natural rubber latex allergy and dental practice. N Z Dent J. 2007;103(4):101-107.
3. Joint Task Force on Practice Parameters; American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma and Immunology; Joint Council of Allergy, Asthma and Immunology. The diagnosis and management of anaphylaxis: An updated practice parameter. J Allergy Clin Immunol. 2005;115(3 Suppl 2):S483-S523.
4. Malamed SF. Medical Emergencies in the Dental Office. 6th ed. St. Louis, MO: Mosby; 2007.
5. Reed KL. Basic management of medical emergencies: recognizing a patient’s distress. J Am Dent Assoc. 2010;141(5 Suppl 1):20S-24S.
6. Hepner DL, Castells MC. Anaphylaxis during the perioperative period. Anesth Analg 2003;97(5):1381-1395.
7. Simons FER, Roberts JR, Gu X, Simons KJ. Epinephrine absorption in children with a history of anaphylaxis. J Allergy Clin Immunol. 1998;101:33-37.
8. Simons FER, Gu X, Simons KJ. Epinephrine absorption in adults: intramuscular versus subcutaneous injection. J Allergy Clin Immunol. 2001;108:871-873.
About the Author
Kenneth L. Reed, DMD
Assistant Director, Advanced Education in General Dentistry
Attending Dentist in Anesthesia, Graduate Pediatric Dentistry
Attending Dentist, Dental Anesthesiology
Lutheran Medical Center
Brooklyn, New York
Clinical Associate Professor
Endodontics, Oral and Maxillofacial Surgery and Orthodontics
The Herman Ostrow School of Dentistry of the University of Southern California
Los Angeles, California
Associate Professor in Residence
University of Nevada Las Vegas
School of Dental Medicine
Las Vegas, Nevada