In the summertime when the weather is fine.

cant effect on the seasonal variation, with a mean shift of 2 months that could be explained by the length of the biological cycle of the mites. The existence of a seasonal pattern for D. pteronyssinus -specific IgE is consistent with previous reports that show seasonal fluctuations in mite counts, or mite allergen concentrations. Mites are very sensitive to fluctuations in humidity and need more than 50% humidity for survival. In the case of Mallorca, the summers are dry and hot. However, in some areas of the world, mite counts increase in the more humid summer months and decrease when the heating season begins in the fall/winter [3] . In tropical regions, mite allergens do not exhibit strong seasonal fluctuations [4] . Therefore, in order to establish, or predict, a cause relationship between specific IgE levels and mite allergen exposure, seasonal patterns of mite allergens should be established. An important question remains unanswered: how large should the reduction in mite allergen levels be to produce a significant decrease in specific IgE levels? Was this level of reduction achieved in this study? This question is difficult to answer based on the present data, since mite allergen levels were not evaluated, and seasonal patterns of mite allergen levels have not been published. Future prospective studies should address this issue. Piacentini et al. [5] analyzed serum IgE and IgG4 in a group of asthmatic children, aged between 7 and 17 years admitted to a residential house located 1,756 m above sea level. This area is known for a very low exposure to mite allergens. All patients were skin prick test positive to at least two of the following allergens: D. pteronyssinus , D. farinae , The production of specific IgE antibodies is a result of sensitization to a specific allergen, or allergens. Specific IgE measurement to Dermatophagoides pteronyssinus is a major diagnostic test for the detection of sensitization against D. pteronyssinus , but its role in predicting the clinical relevance of the allergen is unclear. In general, low IgE antibody levels indicate less probability of clinical disease, while high antibody titers show good correlation with clinical symptoms. The determination of circulating specific IgE antibodies provides a precise evaluation of sensitization to indoor and outdoor allergens. The paper by Hervás et al. [1] , published in a recent issue of International Archives of Allergy and Immunology, shows an interesting relationship between specific IgE levels to D. pteronyssinus and climate parameters. The study was conducted in Mallorca, Spain, from January 1, 2001, to December 31, 2010. The population studied consisted of 24,463 individuals, and 67.2% were positive to D. pteronyssinus . The results showed a marked seasonal pattern of specific IgE levels to D. pteronyssinus which could be significantly correlated with changes in relative humidity and solar radiation [1] . Peak levels occurred from mid-autumn to winter, decreasing to minimum levels in early summer. This correlated with the highest radiation index and the lowest ambient humidity. A previous study in France also addressed the same issue in a large number of patients, obtaining similar results [2] . Benitah et al. [2] analyzed 8,435 measurements spread over 4 years. Significant seasonal and monthly variations were seen every year, with a maximum level in autumn or the beginning of winter. The domestic relative humidity had a signifiPublished online: January 22, 2013