• Itchy raised welts or weals on the surface of the skin.
• The torso, arms, legs and throat are the parts of the body most commonly affected.
• Welts tend to be red towards the edges and have white centres. They resemble a mosquito bite in appearance, but may be substantially larger, varying in size from quite small to 25 cm or greater in diameter.
• Hives tend to occur in batches, with one cluster getting better as another arises and worsens – sometimes in a cycle that continues for days on end. Each individual welt tends to be present for 24 hours or less.
• Symptoms may worsen with each subsequent attack caused by the same trigger.
• Hives that affect the mouth, tongue and throat are referred to as angioedema, and may interfere with breathing. If this occurs seek emergency medical care immediately.
  

Hives are sometimes (but not always) triggered by an allergic reaction to something you have eaten, touched or inhaled, or by an infection or insect bite. The body releases a substance called histamine as part of the immune system response to this trigger, and the high histamine levels make the skin itchy, swollen and inflamed.

In other cases, the same physiological reaction occurs, even though no trigger can be discerned.

Triggers that may provoke hives include:

• Food allergies, especially to strawberries, shellfish, nuts (including peanuts), chocolate, soy, eggs and cheese.
• Reactions to prescribed drugs such as antibiotics and aspirin.
• Certain food additives or preservatives.
• Stress can trigger or exacerbate the problem.
• Insect bites and stings.
• Exposure to hot or cold temperatures or items.
• Exercise and perspiration.
• Pressure on the skin (e.g. from tight clothes).
• Infection, for example with the hepatitis B virus, Epstein-Barr virus (the cause of glandular fever), Candida albicans, or certain bacteria. Infection is a common trigger in children.
• Contact with certain plants (most notably stinging nettles) or animals.

Hives may also be symptomatic of an underlying health problem, such as thyroid imbalance or systemic lupus erythematosus.

• Vitamin C is important for healthy normal immune function and taking vitamin C may help to decrease histamine levels. Take a dose of 250 mg per day or more, over at least three weeks. Some natural health experts recommend even higher doses of 1 g three times a day.
• Taking a combination of B-group vitamins, vitamin C and relaxing herbs may be beneficial during times of ongoing stress.