Hives (urticaria) is a harmless type of rash or skin allergy that is usually caused by an allergy. The rash consists of circular, raised welts on the skin that are usually itchy and occur in batches. Hives can vary in size, from a few millimeters to several centimeters in diameter. Urticaria usually affects the throat, arms, legs, and trunk. About 16% of the population will experience this rash at some time in their lives.

Urticaria, commonly known as hives, is a distressing disorder affecting up to 20 percent of the population at some point in their lives. The swelling that sometimes accompanies urticaria, called angioedema, can lead to swelling of the face, hands, and feet.

Hives may appear at any point on the body once the trigger has happened. This may indicate a cause straight away. For example, if the rash appears on the arms or legs, a sun allergy may be responsible. The rash may have appeared underneath a new ring, which could indicate a reaction to a certain metal contained within the ring.

The rash of urticaria is usually bumpy, red and itchy. The bumps can be the size of mosquito bites to coin-size or larger, and can group together into irregular shapes. The rash will tend to come and go within a few hours, moving from one place on the body to another.

Urticaria occurs following release of histamine, bradykinin, kallikrein, and other vasoactive substances from mast cells and basophils, resulting in intradermal edema from capillary and venous vasodilation and occasionally from leukocyte infiltration. Urticaria has four major mechanisms. Most commonly, it is a manifestation of acute immunoglobulin E (IgE)–mediated hypersensitivity with histamine and other vasoactive peptides released from mast calls and basophils.




Symptoms of hives


Symptoms of urticaria are caused by histamine release from mast cells that exist deep within the skin. Common symptoms include:
• Sudden onset
• Red or skin colored welts that resemble mosquito bites
• Welts change quickly re: size, shape, & location
• Itching


Causes of Hives

Urticaria pigmentosa is one of several forms of mastocytosis, which is caused by excessive numbers of inflammatory cells (mast cells) in the skin. Other forms include solitary mastocytoma (a single lesion) and systemic mastocytosis (involvement in organs other than the skin).
Find common causes and risk factors of Urticaria :
·    Pregnancy.
·    Allergens in food.
·    Heat/cold pressure, exercise.
·    Medicines-painkillers, antibiotics, antihypertensives, codeine.


Treatment of Hives
Some common treatment mehods of Hives:
Apply cool compresses to the welts. This may reduce swelling and pain . If a large part of your body is affected, soak in a cool bath. Avoid hot baths or showers.
Normal-dose antihistamines are often used short-term for acute hives.
The standard treatment for hives and angioedema is antihistamines, which block the symptom-producing release of histamine.
High-dose antihistamines may be necessary in more recalcitrant cases.
In the case of severe symptoms, short courses of oral steroids may be prescribed. Both steriods and antihistamines come in topical solutions as well as systemic forms and these topical forms can also be used to treat hives.
Specialist investigations may be needed in the case of an underlying illness.
Injections of epinephrine - used in cases that involve life-threatening episodes