What is Hives ?
It is defined as a disorder in which there is a skin rash which occurs as dark red, raised and itchy bumps. They are caused due to the allergic reactions and are mainly the non allergic type. They are also referred as an utricaria. The most cases of this disorder which extends up to less than 6 weeks lead to the acute condition of this disorder. They are due to the result of allergic trigger. The most cases of this disorder which extends up to more than 6 weeks lead to the chronic condition of this disorder. They occur hardly due to allergy.
Most of the patients with chronic hives have an unknown cause. There are 30 to 40 percent of the patients which suffer from chronic idiopathic utricaria. It is an auto immune cause. The acute viral infection is common cause of acute utricaria which is also known as the viral exanthema. There are other causes of hives which include the friction, pressure, temperature, exercise and sunlight. There are wheals which are formed in the utricaria and denotes to the raised areas which are surrounded by the red base. They can appear anywhere on the surface of skin. It can be allergic or non allergic.
There is a release of inflammatory mediators including the histamine from cutaneous mast cells which result in the leakage of fluid from blood vessels which are superficial. They can be pin point in size and many inches in the diameter. There is a similar condition known as the angio edema. In this there is a leakage of fluid from the blood vessels. The individual hives are painful and last more than 24 hours. They may leave a bruise as it may lead to the more serious condition known as the utricaria pigmentosa. The hives which are formed due to the stroking skin are due to a benign condition known as the dermato graphism.