Causes of urticaria

Causes of Acute Urticaria

Acute urticaria is a skin disease characterized by breaking out skin changes which are similar to those skin reactions which occur in contact with a nettle. Urticaria rash consists of elevated, reddish or pale skin changes of different sizes and shapes. The rash outbreak is usually accompanied with very severe itching. Skin stains go as quickly as appear, usually for up to 24 hours.

Development of urticaria is caused by mastocytes, located in the subcutaneous tissue, which releases histamine and other mediators of inflammation (prostaglandins, leukotrienes). Urticaria may brake out daily or intermittently with shorter or longer periods without rash outbreak in the period up to 6 weeks, when it is about acute urticaria. If urticaria appears over a period of 6 weeks it is classified as chronic urticaria.

Given that urticaria is defined as skin reactions to different stimuli, the etiology of this disease is different.Causes of acute urticaria include: food ingredients - fish, shellfish, strawberries and other fruits, cheeses, eggs, preservatives, additives, and artificial food colors drugs - drug antigens - especially penicillin, analgesics, Aspirin, insulin, anti-tetanus serum insect poisons

Causes of Contact Urticaria

Urticaria rash occurs at the contact spot with the plant toxins (nettle), toxic marine animals (jellyfish, anemone), insect toxins and drugs. Rash is limited to contact area. The immunologically induced contact urticaria require prior contact with the causative allergens in order for person to become hypersensitive, while non-immune contact urticaria leads to the creation of rash with the first contact. Causes of Physical Urticaria

In physical urticaria mediators of inflammation are released and rash emerges without the participation of immunological mechanisms.

This disorder is caused by various physical stimuli: urticaria to cold, heat urticaria, urticaria in response to sunlight, urticaria which occurs after fever or stress, increased sensitivity to acetyl-choline . Skin changes occur only at the area of the physical factors action, rarely can occur in remote places (reflex urticaria). Usually, these changes are localized and there is no general symptoms. But, in the case of urticaria caused by cold, bathing in cold water may cause generalized changes and anaphylactic shock.

Urticaria Caused by Non-immunological Factors

Urticaria may be caused by non-immunological factors:idiosyncrasies mechanism - direct non-immunological releasing of inflammation mediators from mast cells drugs (morphine, codeine, nonsteroidal anti-inflammatory drugs, acetylsalicylic acid), preservatives neuropeptides - deterioration of urticaria in stressful situationsradio-contrast agents hormones (estrogen, corticotropin).

Causes of Chronic Urticaria

Chronic urticaria shows the emergence of skin changes in a period longer than 6 weeks. If there are periods without rash outbreak, then it is about recurrent chronic urticaria.

Chronic urticaria often occurs in adults, mostly in women in middle age. This disease is a diagnostic and therapeutic problem.

From 0.1 to 3% of the entire population gets chronic urticaria. 25% of patients with acute urticaria develop a chronic form of the disease. The average duration of illness is 3-5 years, while 20% of patients live with chronic urticaria for 20 years.

In 20-30% of cases the cause of the disease may be found: medications (aspirin, anti-rheumatics, an inhibitor of angiotensin-converting) food (2%) preservatives and additives (10%) infection (2-5%) - hepatitis B and C , Helicobacter pylori, parasites, chronic sinusitis malignancies of internal organs physical agents (heat, cold, sunlight, pressure, vibration, water). In 70-80% of cases, chronic urticaria develops because of unknown reason.

Causes of Chronic Idiopathic Urticaria?

Recent discoveries prove that patients with chronic idiopathic urticaria have auto-antibodies in the receptor for IgE antibodies on the mast cell, which confirms the basis of autoimmune diseases.