Urticaria, commonly referred to as hives, is a skin condition characterized by the appearance of weals or angioedema, or in some cases, both. The term “urticaria” is derived from Urtica dioica, the Latin name for the European stinging nettle, which causes a similar reaction when it comes into contact with the skin. Weals present as raised, skin-colored or pale swellings, typically surrounded by redness, and can last from a few minutes to 24 hours. They are often intensely itchy, sometimes accompanied by a burning sensation. Angioedema, on the other hand, manifests as deeper swelling within the skin or mucous membranes, usually resolving within 72 hours. It can be asymptomatic but may cause discomfort in some individuals.
Urticaria is classified as acute when it persists for less than six weeks, often resolving within hours or days. This form of the condition is quite common, affecting approximately one in five individuals at some point in their lifetime, with a slightly higher prevalence among those with atopic tendencies. It occurs across all racial groups and genders.
The underlying cause of acute urticaria involves the release of chemical mediators from tissue mast cells and circulating basophils, which include histamine, platelet-activating factor, and various cytokines. These substances activate sensory nerves, cause dilation of blood vessels, and increase fluid permeability in surrounding tissues. Bradykinin release is responsible for the swelling seen in angioedema. Several theories attempt to explain the mechanisms behind urticaria, including immune system involvement, arachidonic acid pathways, coagulation processes, and genetic predisposition. Serum sickness and related reactions result from immune complex deposition in affected tissues, contributing to the inflammatory response.
Acute urticaria can be triggered by various factors, though in many cases, the exact cause remains unidentified. Common culprits include viral infections such as upper respiratory illnesses, viral hepatitis, and infectious mononucleosis. Bacterial infections, including dental abscesses and sinusitis, have also been associated with urticaria. Certain foods, particularly milk, eggs, peanuts, and shellfish, can induce IgE-mediated allergic reactions leading to hives. Medications, including antibiotics, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), opiates, and radiocontrast media, can also trigger pseudoallergic reactions. Other potential causes include vaccinations, insect stings, and contact with allergens such as rubber latex. In severe cases, allergic urticaria may progress to anaphylactic shock, which can result in life-threatening complications such as bronchospasm and cardiovascular collapse. Isolated angioedema episodes without urticaria may be linked to the use of angiotensin-converting enzyme (ACE) inhibitors.
The clinical presentation of acute urticaria varies in severity and distribution. Weals can be small or several centimeters in diameter, appearing as white or red swellings that may merge into large patches. Their shapes are diverse, ranging from round to targetoid lesions, and they may shift in appearance over time. While urticaria can affect any part of the body, it typically presents as a widespread eruption. In contrast, angioedema is often more localized, frequently involving the face—especially the eyelids and areas around the mouth—along with the hands, feet, and genitalia. In severe cases, it may extend to the tongue, uvula, soft palate, and larynx, posing risks to airway patency. Serum sickness caused by blood transfusions or specific medications can result in urticaria accompanied by systemic symptoms such as fever, swollen lymph nodes, joint pain, and bruising.
Diagnosis of acute urticaria is based on the presence of transient weals lasting less than 24 hours, with or without angioedema. A comprehensive physical examination is necessary to rule out underlying conditions. In cases where food or drug allergies are suspected, skin prick tests, radioallergosorbent tests (RAST), or CAP fluoroimmunoassays may be performed. Histological examination of a skin biopsy can sometimes be challenging, as findings are often nonspecific, showing dermal edema, dilated blood vessels, and a mixed inflammatory infiltrate. When vessel-wall damage is present, urticarial vasculitis may be considered.
Treatment for acute urticaria primarily involves second-generation oral antihistamines, including cetirizine, loratadine, fexofenadine, desloratadine, levocetirizine, rupatadine, and bilastine. These medications are preferred due to their non-sedating properties. If standard doses prove ineffective, the dosage can be increased up to fourfold. Continuous use is recommended until symptoms resolve, rather than taking the medication only when needed. Older first-generation antihistamines such as promethazine and chlorpheniramine are no longer favored due to their sedative effects. In cases of severe urticaria with angioedema, a short course of oral corticosteroids like prednisone may be necessary, though systemic steroids do not significantly hasten symptom resolution.
Pregnant and breastfeeding individuals should avoid systemic treatments unless absolutely necessary, though loratadine and cetirizine have not been linked to birth defects. Certain antihistamines, such as terfenadine and astemizole, are no longer used due to their cardiotoxic effects when combined with ketoconazole or erythromycin. Psychotherapy has been noted to benefit some individuals with chronic urticaria, particularly when stress or psychological factors contribute to symptom exacerbation.
Beyond pharmacological treatment, identifying and avoiding potential triggers is crucial in managing urticaria. Those with known allergies confirmed by positive IgE or skin prick tests should eliminate these allergens from their environment. In individuals with drug-induced urticaria, alternatives such as paracetamol should be used instead of NSAIDs. Cooling the affected skin with fans, cold flannels, ice packs, or soothing moisturizers can provide symptomatic relief.
For cases of refractory acute urticaria, where symptoms persist despite antihistamine therapy, a short course of systemic corticosteroids may be warranted. However, if the urticaria is life-threatening, particularly when involving airway swelling, an intramuscular injection of adrenaline (epinephrine) is required to manage anaphylaxis.
In summary, acute urticaria is a common and often transient condition that can arise from a variety of triggers, including infections, allergens, medications, and environmental exposures. While most cases resolve spontaneously or with antihistamine treatment, severe reactions require immediate medical intervention. Identifying triggers, avoiding known allergens, and using targeted therapy are key strategies for managing urticaria and preventing recurrent episodes.
