Hives, also known as urticaria, are itchy, raised welts on the skin that can vary in size and appear anywhere on the body. They often appear suddenly and can disappear within hours or days.

Common Causes of Hives

Hives are usually triggered by the release of histamine and other chemicals in the skin. Many factors can cause this release, including:

• Allergic Reactions: These are a frequent cause, triggered by allergens such as foods (e.g., shellfish, nuts, eggs), medications (e.g., antibiotics, NSAIDs), insect stings, latex, and pet dander.
• Non-Allergic Triggers: These can include:
• Physical stimuli: Pressure, cold, heat, sunlight, vibration, and exercise can sometimes induce hives. This is known as physical urticaria.
• Infections: Viral (e.g., common cold), bacterial, and fungal infections can sometimes trigger hives.
• Medications: Certain medications can cause hives directly, even if you're not allergic to them.
• Stress: Emotional stress can sometimes be a contributing factor.
• Food additives: Certain dyes and preservatives in foods may trigger hives in some individuals.

Angioedema: Deeper Swelling

Angioedema is a condition that often occurs with hives. It involves swelling in the deeper layers of the skin, often affecting the lips, eyelids, tongue, throat, genitals, and hands or feet. The swelling can be significant and sometimes painful. Like hives, angioedema is usually a result of histamine release.

Hereditary Angioedema (HAE): A Different Mechanism

Hereditary angioedema (HAE) is a rare genetic condition that causes recurrent episodes of severe swelling, primarily in the face, limbs, abdomen, and airway. Unlike typical hives and angioedema, HAE is not caused by histamine release. Instead, it's due to a deficiency or malfunction of a protein called C1 inhibitor, which leads to an overproduction of a peptide called bradykinin. Bradykinin causes fluid to leak from blood vessels into the tissues, resulting in swelling.



Key Differences between Typical Angioedema and HAE:

• Cause: Typical angioedema is usually histamine-mediated, often linked to allergies. HAE is caused by a genetic defect affecting the C1 inhibitor protein and bradykinin production.
• Symptoms: Both involve swelling, but HAE attacks can be more severe and often involve abdominal pain and airway swelling without the itchy welts of hives. Hives are a common feature of typical angioedema but are usually absent in HAE attacks.
• Triggers: Triggers for typical angioedema can be varied (allergens, medications, physical factors). HAE attacks can be triggered by trauma, stress, surgery, dental work, infections, and certain medications.
• Treatment: Typical angioedema is often treated with antihistamines and sometimes corticosteroids. HAE requires specific medications that target the bradykinin pathway or replace the missing C1 inhibitor protein.

If you experience frequent or severe episodes of hives or swelling, especially if accompanied by difficulty breathing or abdominal pain, it's important to seek medical attention to determine the underlying cause and receive appropriate treatment. If there's a family history of swelling attacks without hives, hereditary angioedema should be considered.