Blood will be obtained by venipuncture. The blood samples will be used to estimate the frequency of to estimate the frequency and the products of cells involved in the allergic reaction. We will quantify the number of lymphocytes and their subsets, and the number granulocytes (neutrophils, basophils, and eosinophils) and monocytes and we will analyze their products (such as cytokines, chemokines, prostanoids). Such analysis will be performed doing cytoflow studies, using 4 color flow cytometry (BD FACSCalibur Flow XCytometry System) at the Children's Hospital Flow Cytometry core facilities, ELISA, mRNA analysis and western blots using when indicated the Nucleic Acid/Protein Core. If blood won't be all used up in the aforementioned tests it will be stored in nitrogen liquid for future similar tests or repetition of the ones already performed in case of technical problem with the first attempt.

The Center for Applied Genomics (CAG) will perform genetic analysis. All subjects (cases and controls) have been or will be genotyped on the Illumina HumanHap BeadArray SNP platform, and data has been stored in following an IRB approved protocol

Whole Exon Sequencing (also known as targeted exome capture) is an efficient strategy to selectively sequence the coding regions of the genome as a cheaper but still effective alternative to whole genome sequencing. Exons are short, functionally important sequences of DNA which represent the regions in genes that are translated into protein and the untranslated region flanking them (UTR). It is estimated that the protein coding regions of the human genome constitute about 85% of the disease-causing mutations.

Statistical analysis will be done in conjunction with CAG and Children's Hospital of Philadelphia (CHOP) bioinformatics center. We will compare the genetic variants identified between sequencing and SNPs -based genotyping.

EndoPat is a noninvasive endothelial function assessment. Patient should rest comfortably for 10 minutes prior to the test. Using a standard blood pressure cuff, the brachial artery is occluded for a 5 minute period. When the cuff is released, EndoPat measures blood flow rates pre-occlusion and post-occlusion. This test requires patients to sit still for 15 minutes. It's recommended that the patient fast 3 to 8 hours before the test. In addition, the following drugs should not be used for 24 hours before testing: Nitroglycerine, Alpha-blockers, beta-blockers, and calcium channel blockers, ACE inhibitors, Statins