When they first appear on anybody’s skin, they may not only astonish and upset a person, they may even scare one. Swollen, red, extremely itchy patches on the skin surface arouse deep sympathy for a sufferer, especially if it is a child who becomes a victim of hives.
Hives may vary in shape and size ranging from small red bumps and patches to huge pink rings and wheels with pale center. They can appear on any part of the body, including soles of the feet and palms of the hands, and even mucous membranes. A specific feature of hives is that they often change size, coloring, and place they appear on. They may even mysteriously vanish on their own in some time and appear later on the other part of the body. Sudden onset of the rash is another peculiar feature of urticaria.
Generally, hives are divided into acute, chronic, and single episode disease. Acute urticaria lasts not longer than 6 weeks. If the symptoms do not clear for longer than this time, doctors usually conclude that it is a case of chronic urticaria. Single episode hives may be associated with bacterial and viral infections, or the use of certain medications.
Statistics confirms that 80% of chronic hives cases are idiopathic, meaning that no reason for the development of the disease can be found. Heredity may play a role in a small number of patients with urticaria. A larger amount of the disorder cases is associated with allergic reaction to some substances and objects. However, such disorder’s symptoms are usually short-term.
The most common triggers of urticaria are foods, drugs, pollen, dust, insect bites, etc. They usually provoke an outbreak of acute short-term urticaria.
Foods, which are said to be the most potent allergens, are fish, nuts, eggs whites, citrus fruits, chocolate, cheese, and many others. Besides, many people may develop urticaria in response to foods additives (tartrazine), antioxidants (butylated hydroxyanisole and butylated hydroxytoluene), and preservatives (benzoic acid and benzoates).
As for the drugs, penicillin, aspirin and other NSAIDs, phenobarbital, antibiotics, and some other medications can cause urticaria development and outbreaks.
Scientists also define some types of hives taking into account the underlying cause or trigger of the disease.
Physical urticaria is associated with the skin contact with some substances or objects. The subtypes of physical urticaria include:
- dermographic urticaria (applying pressure to skin or its trauma is its cause);
- cold urticaria (caused by cold water, air, or other cold objects);
- cholinergic urticaria (skin overheating by hot bath, consuming spicy foods or alcohol, exercising, etc. may trigger this type of hives);
- solar urticaria (response to ultraviolet light);
- vibration urticaria (any vibration is its trigger).
Adrenergic urticaria is another type of the disease, caused primarily by emotional stress due to the release of adrenaline, noradrenaline, prolactine, and dopamine.
One more type of hives, which appears to be really dangerous and even life-threatening, is called angioedema. It affects deeper structures and layers of the skin. If it strikes respiratory tract, a patient may have difficulty breathing. Anaphylactic shock may be the result of angioedema.
Perhaps, the most important question is how exactly urticaria develops and what physical mechanisms are involved in this process. Scientists explain that hives are associated with a reaction of body’s immune system to substances and objects, which are perceived by this body’s defense as hostile and dangerous. The matter is that immune system in some people is hypersensitive to certain things (we call them “allergens”); thus it over-responses to them.
During this process a number of chemicals, and histamine in particular, are released in the body, causing fluid from the blood vessels in the spot of the hives trigger action to accumulate under the skin surface. This results in redness, swelling, and itching of the area.
On right are the examples of such complicated body’s processes, which we call so simply – hives.
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