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Hives or urticaria is an extremely common reaction in which there is a break out of bumps or plaques of various sizes. These plaques can appear anywhere on the body. The amount of time that these plaques last also determines the kind of urticaria it is. Those lesions lasting for less than six weeks are called acute urticaria, while those that last for more than six weeks are called chronic urticaria.  

What Is The Pathology Behind Hives?

While the most common cause of hives is allergic in nature, there are other reasons, like infection, an autoimmune reaction, and stress that may cause a hives breakout. It may also be idiopathic in nature, meaning no clear reason has been ascertained.

The basic pathology behind the outbreak, however, is a release of histamine and other inflammatory mediators into the blood stream from mast cells. This histamine changes the permeability of our blood vessels and allows the plasma to filter through. This is what causes the swelling.

Types Of Hives

  • Acute Urticaria: Caused commonly by food allergies (nuts, fish, eggs etc), medication (NSAID’s, blood pressure medication etc) and insect bites.
  • Chronic Urticaria: Usually seen alongside an underlying systemic disease like thyroid infection, hepatitis or even a cancerous growth. Most times however, the exact cause remains undetermined.
The diagnosis of the type of hives and the cause for it is done by an allergist. You may need to undergo a series of patch tests and/or blood tests to determine the cause.
  • Physical Urticaria: This is when a hives like reaction is seen in response to physical activity or stimulation of the skin by heat, cold, light, vibration etc. This is usually short lived and disappears on its own within an hour of cessation of the physical activity.

Differential Diagnosis

There is another condition called angiedema that is also an allergic reaction and may occur at the same time as hives. It is, however, not the same condition. It is in fact much more serious and can be life-threatening as well.

Angiedema causes an inflammatory reaction and associated swelling in the deeper tissues of our body and may cause a constriction of some vital organs. The eyes, mouth, feet, throat and even the stomach are all areas which are affected by angiedema.


The treatment involves the use of over the counter anti-histamine medication which is very effective in resolving the symptoms of hives. If a person has been diagnosed with chronic urticaria, then a long term use of this medication may be prescribed.

If the swelling appears around the vital structures of the body, then your doctor will recommend you keep an epinephrine shot close by at all times so that it can be administered in the time of an emergency.

The long term management also involves a visit to the allergist in an attempt to isolate the potential allergens and thus try and reduce exposure to them.

In some cases of physical urticaria, the doctor will ask you to avoid situations in which there is sudden change of temperature, prolonged period of sun exposure or the use of constrictive clothing for a prolonged period of time.

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