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Don’t Be So Sensitive!
Lindee Abe, APRN, FNP-C, ENP-C
Hypersensitivity reactions can happen to anything in the environment. Likewise, there are many potential triggers. Hypersensitivity reactions are also a common chief complaint. With this being such a common chief complaint, it is essential to be able to quickly develop a treatment plan for these patients based on the type of hypersensitivity reaction and also the evidence for the use of specific treatments.
Before discussing treatment options for a hypersensitivity reaction, let’s review the four types of hypersensitivity reactions. We can break these down into 4 types (I – IV), based on the underlying pathophysiology of the reaction taking place:
| Type | Findings |
| I | Most severe (anaphylaxis) Caused by an IgE-mediated response Can only occur with a subsequent exposure to the offending agent Will not occur on the initial exposure to an agent |
| II | IgG and IgM mediated response Causes a cytotoxic response in the body |
| III | IgG and IgM response Create immunocomplexes that damage the underlying tissue |
| IV | Most commonly seen Cell-mediated delayed hypersensitivities Typically occur between 24 and 48 hours after exposure to an allergen |
Epinephrine is First Line!
Generally speaking, the quicker a hypersensitivity reaction occurs, the response will likely be more severe. Type I hypersensitivity reactions are a true medical emergency. They happen within minutes of exposure to the agent and also progress rapidly. However, anaphylaxis will not always result in death if untreated. That being said, the risk of death is significant and it should be treated whenever possible. Treatment for Type I reactions is epinephrine. Epinephrine is the only medication that will effectively treat a Type I reaction response taking place in the body. This is important because there is no other medication that will provide the same results as epinephrine.
Epinephrine stops the release of histamine that occurs during the Type I hypersensitivity reaction. Histamine will cause inflammation and swelling in the body, leading to airway constriction and also peripheral vasodilation. The earlier your patient receives epinephrine, the less histamine they release in the system. This in turn leads also to improved patient outcomes. Epinephrine also causes vasoconstriction and relaxes the smooth muscle of the airway, which counteracts the bronchospasm and hypotension that occurs with anaphylaxis.
Dosing
The dose for epinephrine is based on weight:
- >50 kg, the dose is 0.5 mg.
- >25 kg and <50 kg, the dose is 0.3mg
- Children weighing > 10kg and < 25 kg, the dose is 0.15 mg
- Infants weighing under 10 kg, the dose is 0.01 mg/kg.
This is for dosing in the clinic/hospital based on the 1mg/mL, or the 1:1,000 concentration, since it is an intramuscular injection. Remember that epinephrine also comes in the 1:10,000 strength utilized during ACLS. The epinephrine auto-injectors come in two different dosages, 0.15mg for pediatric patients and also 0.3mg for adult patients. There are also no contraindications for giving epinephrine in an hypersensitivity reaction.
Prescriptions
If you prescribe your patient auto injectors, give them two. You should also show them how to use the injector and allow them to use a practice injector if needed. Instructions related to the epinephrine autoinjector should also include that they should hold the injector in place for 10 seconds. This will ensure the maximum delivery of medication. They also should know to repeat the injection if symptoms are not improving in 5-15 minutes. The preferred location for Injection is the lateral thigh. You can also inject this through clothing. They should also note the expiration date of the injector to set a reminder in their phone or other calendar to avoid having outdated medication. Tell your patients to seek emergency care after administration of the auto-injector, as they will also need ongoing monitoring, and may need more treatments.
Adjunct treatments for Hypersensitivity Reactions
You can also give other medications with epinephrine to help reduce rebound and recurrence.
H1 receptor blockers
- Most commonly diphenhydramine 25-50 mg
- Can be given for urticaria.
H2 receptor blockers
- Famotidine 20mg
Glucocorticoids
- Methylprednisolone 125mg IV or IM.
Bronchodilators
- Help alleviate bronchospasm
The data supporting these adjunct treatments is mixed. There is also no definitive evidence for their benefit. When symptoms rebound after you have given your patient IM or IV epinephrine, consider and epinephrine infusion. Other vasopressors can also be used. Patients on beta-blockers may not have the desired clinical response to epinephrine and may also benefit from glucagon administration.
Monitoring Hypersensitivity Reactions
There is also the consideration of how long to monitor patients after administration of epinephrine for a Type I hypersensitivity reaction. It seems that the length of stay varies between providers. Patients receiving ongoing treatment or having refractory symptoms will need a longer length of stay and also admission. The phenomenon of biphasic anaphylaxis can occur in up to 20% of cases, where the patient initially responds to treatment and then has a worsening of their condition. There are recommendations of observation of up to 24 hours after epinephrine for possible biphasic reaction, but there is evidence that shows 10 hours is likely sufficient. The American Academy of Family Physicians recommends an observation period of 4 to 12 hours, longer for more severe reactions.
Type IV Hypersensitivity and Contact Dermatitis
Type IV hypersensitivity reactions are the most commonly seen type of reaction in clinics. This can occur at any time of exposure and is facilitated by T-lymphocytes. A patient may have been using the same detergent for years and then develop a reaction to it. There are three types of Type IV hypersensitivity, including contact dermatitis, tuberculin-type hypersensitivity, and granulomatous-type hypersensitivity.
Contact dermatitis is the condition most commonly encountered in the clinical setting. The primary treatment for it is removal of the offending agent. Common contact allergens include plants, nickel, and also cosmetic products. Topical steroids can also be used for relief of urticaria, or in more severe cases oral corticosteroids. In cases where greater than 20% of the total body surface area is involved, oral corticosteroids should be utilized. Topical calcineurin inhibitors, phototherapy, and systemic immunosuppressive agents may also help.
Takeaways for Hypersensitivity Reactions
The key take home point is to emphasize that in Type I hypersensitivity reactions there is no alternative to epinephrine. Epinephrine is the only medication that can make a difference in the clinical outcome of the patient. It should be used as soon as possible for the maximum benefit to the patient. Clinicians and patients should also be educated on the use of administration of epinephrine. Patients should also feel comfortable administering epinephrine through auto-injectors and receive all the necessary education surrounding the administration.
References:
Brod, B. (2020). Management of Allergic Contact Dermatitis. Retrieved from https://www.uptodate.com/contents/management-of-allergic-contact-dermatitis search=contact%20dermatitis%20treatment&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2.
Campbell, R. & Kelso, J. (2021). Anaphylaxis: Emergency Treatment. Retrieved from https://www.uptodate.com/contents/anaphylaxis-emergency treatment#:~:text=Situations%20requiring%20caution%20%E2%80%94%20There%20are,22%2D26%2C45%5D.
Kemp SF. The post-anaphylaxis dilemma: how long is long enough to observe a patient after resolution of symptoms? Curr Allergy Asthma Rep. 2008 Mar;8(1):45-8. doi: 10.1007/s11882-008-0009-7. PMID: 18377774. Retrieved from https://pubmed.ncbi.nlm.nih.gov/18377774/.
Marwa K, Kondamudi NP. Type IV Hypersensitivity Reaction. [Updated 2021 Nov 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK562228/. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK562228/#:~:text=There%20are%20three%20subtypes%20of,%2C%20and%20granulomatous%2Dtype%20hypersensitivity.
Menachof, M. (2021). What are the Four Types of Allergic Reactions? Retrieved from https://www.advancedentdenver.com/blog/four-types-of-allergic-reactions/.
Pflipsen, M. & Colon, K. (2020) Anaphylaxis: Recognition and Management. Am Fam Physician. 2020 Sep 15;102(6):355-362. Retrieved from https://www.aafp.org/afp/2020/0915/p355.html.
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