الفهرس 
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Abstract
Chronic urticaria is characterized by the occurrence of daily or almost daily wheals and\or angioedema lasting more than 6 weeks. CU is classified according to the etiology into chronic spontaneous and chronic inducible urticaria. The cause of CSU is unknown in 50% of patients, 30% to 40% of patients have autoantibodies, suggesting an autoimmune basis. Other causes include infections, drugs, food and food additives, endocrine and malignant diseases. Stress can play a role in the etiology.
In most temperate humid areas of the world, house dust mites are a major source of allergens present in house dust. Mites sensitize and induce allergic disorders such as allergic rhinitis and asthma in predisposed individuals. In addition, house dust mites are important deteriorating factors in patients with atopic dermatitis. SPT and sIgE assays are the most commonly used diagnostic tools for confirming sensitization.
In the current study, 100 patients with CSU were investigated for any apparent cause. After exclusion of any etiological factor that might cause CU, the role of mite sensitivity was tested using SPT and SIgE. We studied two types of HDM allergens; Der. P. and Der. F. The severity of urticaria was assessed using the UAS.
Our study demonstrated 33 % prevalence of positive SPT to Der. P, 37% to Der. F. and 39% overall prevalence. 52% of the patients had positive SIgE result to Der. P. and 67% had positive SIgE result to Der. F. The results of sIgE were higher than that of SPT. The overall mite sensitivity in the group of CU alone was 29.2 % while in the group of CU with other atopic diseases it was 64.3 %.
Comparing the UAS in mite sensitive and mite non-sensitive groups revealed no significant statistically difference (P > 0.05), However 41% of the mite sensitive group had sever urticaria, 28% had moderate urticaria and 26% had mild urticaria, while only 5% had well controlled disease.
In summary, our study showed that the prevalence of mite sensitivity in patients with CU was common and it may be a provoking factor in CU. CU Patients with atopic disorder are more likely to be sensitive to mites than patients with CU alone. We suggest further studies with larger samples studying the effect of mite elimination and the effect of specific hyposensitization therapy.