What Is the Main Cause of Urticaria?

Urticaria causes intensely itchy red raised bumps on the skin.

Urticaria is the medical term for hives, which is a skin reaction characterized by smooth, slightly raised bumps that are red and often itchy. Most of the time, hives are temporary and will go away on their own within several hours or a few days at worst, though they may recur over several weeks. If episodes of hives last longer than 6 weeks, it is considered chronic urticaria.

Urticaria (hives) are a sign in themselves, characterized by the following:

• Bumps or wheals are pale, red, and swollen.
• Bumps vary in size from a pencil eraser to a dinner plate.
• Wheals are mostly circular raised patches of skin and sometimes form a bull's-eye pattern.
• When several hives join together in a larger area, this is called a plaque.
• Bumps usually appear suddenly.
• Hives usually cause itching.
• Hives may sometimes burn or sting.
• Urticaria may appear anywhere on the body.

In about half of patients with acute urticaria, the main causes typically include allergies:

• Food allergies
  • Common foods that cause allergic reactions and urticaria include peanuts, tree nuts, shellfish, and eggs.
• Drug allergies
  • Almost any drug can cause an allergic reaction, the most common are the following:
    • Nonsteroidal anti-inflammatories (NSAIDs)
    • Aspirin
    • Angiotensin-converting enzyme (ACE) inhibitors
    • HIV medications
    • Anti-seizure medications (anticonvulsants)
    • Penicillin antibiotics
    • Sulfa antibiotics
• Physical contact (contact urticaria)
  • Refers to an allergic reaction caused by a substance that comes into contact with the skin
• Insect bites or stings
• Hypersensitivity reactions
  • May occur from substances that are ingested, inhaled, or injected

Urticaria may also result from nonallergic reactions to substances that cause the body to react in ways similar to an allergic reaction. These are causes of nonallergic hives:

• Certain drugs
  • Narcotics (opiates), succinylcholine, and certain antibiotics
• Certain food and beverages
  • Spoiled fish, aged cheeses, or red wine are frequent culprits.
• Certain venoms

Medical causes for urticaria include the following:

• Infectious diseases
  • Viral infections such as acute viral syndromes, hepatitis (A, B, and C), Epstein-Barr virus, and herpes simplex virus.
  • Streptococcal infection
  • Chronic parasitic infections
• Hormonal changes
  • Oral contraceptive use or changes in the menstrual cycle
  • Pregnancy
  • Caused by endocrine tumors or ovarian pathology (rare)
• Lymphoma
  • Urticaria with itching may be a symptom of lymphoma
• Hypothyroidism and hyperthyroidism
• Systemic lupus erythematosus, rheumatoid arthritis, juvenile rheumatoid arthritis, or other rheumatologic diseases (rare)

The following are physical causes of urticaria:

• Cold
• "Cold urticaria" is a rare disorder that causes hives when the skin is exposed to cold. It may be genetic or acquired due to viruses or other illness such as cancers or hepatitis.
• Heat
• Sunlight
• Pressure
• Vibration
• Exercise
• Emotional stress
• Scratching (dermographism)
• Water

Doctors diagnose acute urticaria based on the patient's history and a physical examination. Your doctor may order any of these tests to help diagnose the cause of the hives:

• Skin allergy tests or radioallergosorbent assay test (RAST) (specific IgE) may be indicated if food allergies or hypersensitivity to insect bites is suspected. Generalized allergy tests are not typically recommended.
• Physical challenge tests may be performed if a physical cause is suspected. Patients are exposed to the suspected stimuli (heat, sunlight, exercise, cold, etc.) to see if a reaction occurs.
• Your doctor may perform a skin biopsy if lesions do not resolve in patients who have urticarial vasculitis, a rare condition characterized by inflammation of the blood vessels.

Treatment for urticaria depends on the cause. If the cause of the hives is identified, the easiest way to treat it is to avoid the trigger.

The following medications may control itch of hives:

• Antihistamines (H1 antagonists) such as diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), hydroxyzine (Vistaril), loratadine (Claritin, Alavert), fexofenadine (Allegra), desloratadine (Clarinex), and levocertirizine (Xyzal)
• H2 antagonists such as famotidine (Pepcid) and cimetidine (Tagamet) are not usually used alone for hives but may be combined with an antihistamine (H1 antagonist), because the combination may be more effective than an antihistamine alone.
• Corticosteroids such as prednisolone (Pediapred, Orapred, Millipred), methylprednisolone (Medrol, DepoMedrol, SoluMedrol), and prednisone (Deltasone, Rayos)
• Sympathomimetics such as epinephrine (Adrenalin, Epi-Pen) are often used for severe hives or anaphylactic reactions.
• Tricyclic antidepressants such as doxepin (Silenor, Zonalon, Prudoxin)
• Monoclonal antibodies such as omalizumab (Xolair)
• Immunomodulatory and anti-inflammatory therapy such as cyclosporine (Sandimmune, Neoral, Gengraf), colchicine (Mitigare, Colcrys), and dapsone (Aczone)
• Lukotriene receptor antagonists such as montelukast (Singulair) and zafirlukast (Accolate) are still being studied as a treatment.

Other treatments for hives include the following:

• Keeping a food and symptom diary if reactions to foods or physical causes such as exercise or heat are suspected
• Avoidance of triggers

Acute urticaria may develop into life-threatening swelling beneath the skin (angioedema) and/or a severe allergic reaction (anaphylaxis/anaphylactic shock) very quickly. These are medical emergencies and require immediate medical attention.

Symptoms and signs of anaphylaxis include the following:

• Respiratory distress
• Wheezing or stridor
• Trouble talking
• Low blood pressure (hypotension)
• Fainting
• Rapid heart rate
• Face, lip, mouth, or tongue swelling
• Swallowing problems
• Gastrointestinal distress such as vomiting, diarrhea or abdominal pain
• Joint swelling and/or pain

Call 911 or go to an emergency department if any symptoms of a severe allergic reaction occur.

The primary way to prevent urticaria is to identify the cause and avoid it. Taking medications to stop the allergic reaction as soon as symptoms start can limit the severity of urticaria. Desensitization to allergens or urticaria triggers also may be helpful.