URTICARIA

Urticaria also called nettle rash or hives or wheals in common language simply means itching with rash. It is an allergic skin disorder. It refers to a group of disorders affecting adults and children, in which red patches and wheals occur on the skin.

The release of chemicals such as histamine from mast cells in the skin causes small blood vessels to leak and result in tissue swelling. The wheals can be a few millimeters or several centimeters in diameter, colored white or red, often surrounded by a red flare, and frequently itchy. Each wheal may last a few minutes or several hours, and may change shape. Wheals may be round, or form rings, a map-like pattern or giant patches.

The surface wheals may be accompanied by deeper swellings of eyelids, lips, hands and so on. The swelling is called angioedema. Angioedema may occur with or without urticarial wheals. Angioedema can cause disabling swelling of internal organs, life-threatening blockage of air passages, or severe, uncontrollable intestinal contractions. If the swelling occurs in the throat, it can cause suffocation.

These eruptions can remain on the body for variable periods, anywhere between a few seconds to even hours. They have a tendency to disappear and reappear. They tend to disappear without leaving behind any trace.

Different types of urticaria or hives or nettle rash are as follows :

• Allergic urticaria : When an allergen invades or irritates your body, it unleashes chemicals known as histamines. Some people react to a high histamine level by developing the rash we call hives.
• Non allergic urticaria
• Acute urticaria : It may be caused by an allergy and can last between several hours to many weeks. The most likely triggers for acute urticaria are allergies to pets, horses, latex and foods, such as shellfish and nuts in adults and eggs and cow's milk in children.
• Chronic urticaria : It is not usually caused by an allergy. It refers to hives that persists for 6 weeks or more. There are no visual differences between acute and chronic urticaria. The cause of chronic urticaria is often more difficult to identify. Most cases are called chronic idiopathic urticaria, which means they are caused by the body's unexplained development of antibodies to itself (auto-antibodies or auto-immune).
• Drug induced urticaria : Certain drugs like anti diabetic sulphonylurea glimepride (trade name Amaryl), aspirin, penicillin, sulfonamides and anticonvulsants and so on.
• Physical urticaria : It is triggered by physical factors and lasts only an hour or two and is often categorized into the following :
  • Aquagenic : Reaction to water.
  • Cholinergic : Reaction to body heat, such as when exercising or after a hot shower.
  • Cold (Chronic old urticaria) : Reaction to cold, such as ice, cold air or water.
  • Delayed pressure : Reaction to standing for long periods, bra straps, elastic bands on undergarments, belts.
  • Dermatographic : Reaction when skin is scratched.
  • Heat : Reaction to hot food or objects.
  • Solar : Reaction to direct sunlight.
  • Vibration : Reaction to vibration.
  • Adrenergic : Reaction to adrenalin / noradrenalin.

"In chronic cases, the itchiness may cause sleepless nights and leads to depression."

The rash is very itchy and consists of a number of raised bumpy wheals surrounded by red skin. Ordinary urticaria tends to move about or migrate all over the skin surface.

The condition tends to settle and then relapse again at times of viral illness, stress and after taking medication that contains aspirin. This chronic pattern may recur for many years.

Tissue swelling, called Angioderma, may occur with urticaria. This affects the lax tissues around eyelids, lips, neck and groin.

A careful case analysis and evaluation is required to make a correct diagnosis. There is no need for specific investigations in most of the cases of urticaria. However, these tests may be helpful in some cases :-

• Complete blood count to identify eosinophilia caused by allergy or parasitic infestation, and low WBC from SLE.
• Thyroid antibodies and function in chronic urticaria.
• Comprehensive allergy screening. Blood tests for specific allergy (RAST, or radiollergosorbent tests, or CAP fluoroimmunoassay).
• Skin biopsy if wheals are prolonged.