The influenza virus, commonly known as the flu, is a respiratory illness that can cause a range of symptoms from mild to severe. Hives, also known as urticaria, are raised, itchy welts on the skin that often result from an allergic reaction. While the flu is primarily associated with symptoms like fever, cough, and body aches, a less common manifestation can include skin reactions such as hives.
The Link Between Flu and Hives
The appearance of hives during or after a flu infection is not typically a direct allergic reaction to the virus itself, but rather a result of the body’s immune response. When the influenza virus enters the body, the immune system mounts a defense to fight off the infection. This process involves the release of various inflammatory mediators, including histamine. The excessive release of histamine can lead to hives.
Viral infections, including influenza, are recognized causes of hives, particularly in children. Hives can sometimes appear a week or two after the illness begins. In some instances, hives may even be the only noticeable symptom, especially if the body has some pre-existing immunity to the specific viral strain. While a rash is an uncommon flu symptom, occurring in about 2% of influenza A cases, it is a recognized, albeit indirect, manifestation of the body fighting the infection.
Hives as a Medication Side Effect
Hives appearing during a flu illness can also stem from medications taken to alleviate flu symptoms, rather than solely from the viral infection itself. Many over-the-counter and prescription drugs commonly used for flu, such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin, and even acetaminophen, can trigger allergic reactions. Antibiotics, if prescribed for a secondary bacterial infection, are also a frequent cause of drug-induced hives.
Drug rashes can range from mild hives to more severe reactions, and they can develop immediately or several days or weeks after starting a new medication. It is important to consider any recent medication use when hives emerge during an illness, as this provides an important differential diagnosis. If a rash is suspected to be medication-induced, discontinuing the medication and consulting a healthcare provider is generally advised.
When to Seek Medical Care for Hives
While many cases of hives are mild and may resolve on their own, certain symptoms warrant immediate medical attention, especially when associated with the flu. Difficulty breathing, swelling of the face, lips, or throat (angioedema), dizziness, or a sudden drop in blood pressure can indicate a severe allergic reaction known as anaphylaxis.
Medical care should also be sought if hives are widespread, rapidly spreading, or accompanied by other concerning symptoms like a high fever that does not respond to medication, severe itching that disrupts sleep, or joint pain. Persistent hives, lasting more than a few days or recurring frequently, also warrant evaluation by a healthcare professional to determine the underlying cause and appropriate management.