From the Guidelines
Hives are primarily caused by the release of histamine and other chemicals from mast cells in the skin, often due to allergic responses, infections, stress, or certain medical conditions, and can be triggered by various factors including foods, medications, insect stings, and physical triggers. The exact cause of hives can vary widely among individuals, and in many cases, the cause remains idiopathic even after thorough investigation, as noted in a study published in the British Journal of Dermatology 1. Some common triggers include:
- Allergic responses to foods like nuts, shellfish, eggs
- Medications such as antibiotics, NSAIDs
- Insect stings
- Latex
- Physical triggers like pressure, cold, heat, or sunlight
- Infections
- Stress
- Certain medical conditions like thyroid disorders or lupus
It's also important to consider that at least 30% of patients with chronic urticaria appear to have an autoimmune etiology, as suggested by the presence of histamine-releasing autoantibodies 1. For patients experiencing hives, it's crucial to identify and avoid triggers when possible, and for mild cases, over-the-counter antihistamines like cetirizine, loratadine, or diphenhydramine can provide relief, as can cool compresses and loose clothing to soothe symptoms. However, if hives are severe, persistent, or accompanied by symptoms like breathing difficulties or swelling of the face or throat, immediate medical attention is necessary due to the potential for anaphylaxis, a life-threatening condition that requires emergency treatment with epinephrine, as emphasized in guidelines for the management of anaphylaxis 1. In cases where the cause of urticaria or angioedema is unclear or when symptoms persist, consultation with an allergist-immunologist is recommended for thorough evaluation and management, including possible skin testing, physical challenges, and optimal pharmacotherapy, as outlined in referral guidelines for urticaria and angioedema 1.
From the Research
Causes of Hives
Hives, also known as urticaria, can be caused by a variety of factors, including:
- Allergic reactions to food, medications, or insect stings 2
- Autoimmune disorders, such as autoimmune hypothyroidism (Hashimoto's disease) 2, 3
- Infections, such as Helicobacter pylori 4
- Physical factors, such as pressure, temperature, or vibration 4
- Idiopathic causes, where no underlying cause can be identified 2, 5
Pathogenesis of Hives
The pathogenesis of hives involves:
- Mast cell activation, leading to the release of histamine and other vasoactive mediators 2
- Increased vascular permeability, resulting in edema, erythema, and pruritus 2
- Autoantibodies against the high-affinity IgE receptor or IgE, which can contribute to chronic urticaria 2, 3
Types of Hives
There are two main types of hives: