Urticaria, commonly known as hives, is a skin reaction characterized by the sudden appearance of raised, intensely itchy welts called wheals. These lesions are typically red or skin-colored, ranging from a few millimeters to several centimeters in diameter, and blanch (turn white) when pressed. When hives appear alone or alongside a fever, a viral infection is one of the most frequent causes of this acute reaction. This skin manifestation is a visible consequence of the body’s systemic immune response to the invader, not the virus attacking the skin directly.
The Immune System’s Response to Viral Invaders
The appearance of hives results from the immune system mobilizing defenses against a viral pathogen. When the body detects a virus, it releases chemical messengers to coordinate the immune response, leading to inflammation necessary for clearing the infection.
A central event in this process is the activation of specialized immune cells in the skin, known as mast cells. These cells store chemical mediators, primarily histamine, in small granules. The systemic inflammation and immune signaling caused by the virus can trigger mast cells to degranulate, releasing histamine into the superficial layer of the skin, the dermis.
Histamine acts directly on local blood vessels, causing capillaries to dilate and become temporarily more permeable. This increased permeability allows fluid (plasma) to leak out of the vessels and accumulate in the surrounding tissue. This fluid accumulation produces the characteristic swelling and elevation of the wheals, while histamine stimulates nerve endings, causing intense itching (pruritus).
Specific Viruses Known to Trigger Hives
Many different types of viruses can provoke the immune reaction that leads to acute urticaria. Infections of the upper respiratory or gastrointestinal tracts, such as influenza or the common cold, are among the most common triggers, especially in children. The rash often coincides with the peak of the systemic illness, reflecting the heightened immune activity during that period.
Infectious mononucleosis, typically caused by the Epstein-Barr Virus (EBV), is a well-known culprit for inducing hives due to the robust immune response it generates. Other viruses from the herpes family, including Cytomegalovirus and Human Herpesvirus 6, are also frequently implicated.
In adults, hepatitis viruses (particularly Hepatitis B and C) are more commonly associated with the onset of hives. The SARS-CoV-2 virus (COVID-19) has also been documented as a trigger, with hives sometimes being one of the earliest skin manifestations.
Management and Timeline of Viral-Induced Urticaria
The timeline for viral-induced hives is generally favorable, as the condition is typically acute. Acute urticaria lasts for less than six weeks, and when triggered by a virus, the hives usually resolve completely once the underlying infection clears. Most cases subside within a few days to a few weeks, which is a key difference when compared to chronic hives that persist beyond the six-week mark.
The primary goal of management is to relieve the bothersome symptoms until the wheals disappear on their own. The most effective treatment involves over-the-counter second-generation H1 antihistamines, such as cetirizine or loratadine, which work by blocking the effects of the released histamine. If the standard dose of these non-sedating medications does not provide sufficient relief, a healthcare provider may recommend increasing the dose up to four times the usual amount.
For immediate comfort, cool compresses or taking a cool shower can help reduce localized heat and itching. Patients should also avoid non-specific triggers, such as excessive heat, alcohol, or tight clothing, as these factors can sometimes worsen the severity of the hives.
While most viral-induced hives are benign, seek immediate medical attention if the rash is accompanied by signs of a severe reaction. These symptoms indicate a dangerous systemic reaction requiring emergency care:
- Difficulty breathing
- Wheezing
- Swelling of the tongue or throat (angioedema)
- Dizziness