A 39-year-old male with a past medical history of psoriasis presented with a rash two days after receiving an influenza vaccine. The rash was described as non-pruritic red raised blotches scattered on his face, arms, and chest. A cell phone picture was consistent with a morbilliform rash. The patient sought care at an urgent care facility and was started on antihistamines. The rash resolved within four hours. Importantly, the patient did not report any symptoms suggestive of a severe allergic reaction, such as lip swelling, tongue swelling, throat closing, shortness of breath, wheezing, vomiting, or abdominal pain. He denied any previous reactions to influenza vaccines and had not started any new medications. He also reported no fever, chills, or cough, and no changes in soaps, lotions, or detergents.
The patient reported a chronic sore throat for months, suspected to be due to reflux, for which he is currently taking esomeprazole. He is also on PrEP and Skyrizi for his psoriasis. The medical professional suspected a delayed hypersensitivity rash and addressed the patient's concern about receiving the influenza vaccine the following year.
Delayed Hypersensitivity and Vaccine Reactions
It is unlikely that the observed rash was related to IgE-directed antibodies against the influenza vaccine due to its onset two days after exposure. While the possibility of an allergy to vaccines exists, it's not definitively established in this case. In a recent article published in the Journal of Dermatology and Dermatologic Surgery, several cases of urticaria (hives) following COVID-19 vaccination were reviewed. These hives typically appeared between 1-2 weeks after the vaccination and often persisted for months.
Understanding Hives (Urticaria)
Hives, or urticaria, are characterized by an itchy rash that can appear on the skin. Each individual itchy bump or patch usually lasts a few minutes to a few hours. While each spot may appear and disappear within 24 hours, the overall rash can persist for weeks, and in rare cases, even years. The spots on the skin, known as wheals, form due to histamine being inappropriately released within the dermis. This is why antihistamine medications are effective in managing hive symptoms.
It is crucial for patients to understand that hives are often not caused by allergies, and allergy testing may not yield helpful results. Hives are most frequently a non-allergic immune system reaction. They can be triggered by antibodies produced following an upper respiratory infection (like the common cold) or, as noted in the aforementioned paper, sometimes in response to vaccination. Other triggers include stress, physical stimuli such as pressure, cold, or water. True allergic reactions causing hives are typically linked to foods, medications, or proteins like pet dander.
While most forms of hives are not life-threatening, the rash can be intensely itchy and distressing. The majority of hives resolve within 6 weeks. Hives lasting longer than 6 weeks are termed "chronic," though this duration does not necessarily indicate the underlying cause or prognosis.
Managing Hives and Other Rashes
Starting with non-sedating antihistamines, such as Claritin, is a good initial approach for managing hives. If you are experiencing difficulties in controlling your hives, consulting a dermatologist experienced in skin diseases and their treatments is recommended. It is also important to consider that the rash may not be hives but another dermatological condition. Therefore, a proper evaluation of the specific rash and previous treatments is essential.
Several effective prescription medications are available for treating chronic hives. For further reading on the topic, a comprehensive review on urticaria can be found in the Journal of the American Academy of Dermatology (Antia et al., 2018).
Influenza Vaccine Safety and Potential Side Effects
Flu vaccines have a strong safety record. They typically contain either inactivated virus (meaning the viruses are no longer infectious) or a particle designed to mimic the influenza virus for the immune system. Like any medical product, vaccines can cause side effects. Some studies have indicated a potential small association between injectable flu vaccines and Guillain-Barré syndrome (GBS), estimating the risk at fewer than 1 or 2 cases per million people vaccinated. However, other studies have found no such association, and GBS can also rarely occur after the flu illness itself, with the risk being higher following the illness than the vaccination.
Life-threatening allergic reactions to the flu shot are rare. In the event of a suspected severe allergic reaction or other emergency, it is advised to call 9-1-1 and proceed to the nearest hospital. Reactions should be reported to the Vaccine Adverse Event Reporting System (VAERS). Individuals who believe they have been injured by a flu vaccine may be eligible for compensation from the federal government under specific criteria.
Covid-19 and Flu vaccines - Boost your immunity with winter animation (2022)
The CDC recommends annual flu vaccination for everyone 6 months of age and older, with rare exceptions. A variety of flu vaccines are available, suitable for different age groups. The CDC and the Food and Drug Administration (FDA) continuously monitor the safety of vaccines used in the United States through systems like VAERS, which serves as an early warning system for potential issues following vaccination. Anyone can report possible vaccine side effects to VAERS.
Regarding egg allergies, individuals with egg allergy can receive any flu vaccine (egg-based or non-egg-based) that is otherwise appropriate for their health status and age. Previously, those with severe egg allergies (experiencing symptoms beyond hives) were advised to get vaccinated in a medical setting. However, starting with the 2023-2024 season, additional safety measures are no longer recommended for flu vaccination of people with egg allergies beyond those standard for any vaccine receipt.
