A man dining at an ocean front restaurant decides to order a shrimp cocktail for an appetizer; however, thirty minutes after ingesting the shrimp, he develops a bizarre skin sensation. He feels an intense urge to scratch his skin and he notices that red welts have begun to develop all over his body. This is the classic presentation of urticaria: a common skin disorder in which a red rash develops as a result of an allergic trigger. This condition is also known as hives, and statistics show that 1 in 5 people are affected by this syndrome. Acute urticaria typically lasts less than 6 weeks, but in a subset of patients, it can become a chronic illness. It is a relatively painless but extremely itchy rash which can oftentimes interfere with daily activities such as work and sleep. Interestingly, urticarial lesions are not always allergic in nature. In fact, there are several diseases and physical conditions that can cause the development of hives. In addition to this, although urticaria is a separate entity from anaphylaxis (a life-threatening allergic reaction in which there is swelling of the throat), they can occur concomitantly. Therefore, not only should patients be able to identify urticarial lesions, but also they should recognize when the condition is affiliated with anaphylaxis, given that if the latter is present, both treatment and severity will vary significantly.
Urticaria occurs when the body is exposed to an agent that triggers an inflammatory reaction, and when this response ensues, there is an activation of the body’s immune cells. Subsequent to this, immune cells release histamine, an organic compound which causes localized swelling and an itching sensation. [Medically speaking, histamine enables white blood cells to fight off pathogens or infected cells.] The most commonly described triggers for urticaria include: medications, such as antibiotics in the penicillin class; food sources such as milk, peanuts, and shellfish; latex; plant products; parasitic infections; and insect bites. Other notable triggers include physical factors such as exposure to cold temperatures, sunlight, pressure to the skin, and exercise. Of note, in a large number of cases, the inciting agent is never found. The characteristic manifestation involves a series of red rounded lesions dispersed all over the body. These may enlarge within minutes to hours and once the lesions resolve, they leave no skin markings. The diagnosis of urticaria is clinical and is based on the patient’s history and a physical examination. Urticaria is treated with anti-histamine medications (e.g. Benadryl) and oral steroids which suppress the inflammatory reaction. Furthermore, if the doctor suspects an allergic cause, the patient will be referred to an allergy specialist for advanced testing.
Urticaria can also be the initial presentation of a disease, as is seen in lupus, rheumatoid arthritis, and thyroid disease. Yet, this is a less common scenario. Luckily, isolated hives is considered a benign condition, and in ⅔ of cases urticarial lesions will resolve spontaneously. Moreover, for patients with persistent lesions, basic symptomatic treatment will generally suffice. On the other hand, if urticarial lesions occur in conjunction with anaphylaxis (where patients manifest difficulty swallowing due to swelling of the oral structures) patients will require emergency treatment and prompt hospitalization.