Vitamin D deficiency (VDD) has been reported in very high rates in the U.S. population. Deficiency has been implicated in various diseases such as diabetes, high blood pressure, cardiovascular disease, and many cancers. It has also been implicated in several allergic disorders and immune system dysregulation. The National Health and Nutrition examination survey (NHANES) in 2005-2006 was a cross-sectional survey performed in the noninstitutionalized population of the United States by the Center for Disease Control and Prevention and National Center for Health Statistics. It consists of an extensive interview performed at home and an examination performed at a mobile center. An allergy questionnaire was provided as interview data on self-reported allergic diseases including allergic rhinitis, allergies, and atopic dermatitis. Data were collected using the question, "Has the doctor or other health professional ever told you that you have allergies?" The laboratory parameter of vitamin D < 10 ng/mL was used to define severe VDD. The data were analyzed by logistic regression with SAS Version 9.1 (SAS Institute, Inc., Cary, NC) using the Procedure survey methods. Of 10,348 people who participated in the 2005-2006 NHANES survey, our final sample consisted of 4979 people in whom serum 25-hydroxyvitamin D levels were completed after excluding subjects <20 years of age and those with missing vitamin D values. The VDD was positively correlated with prevalence of allergies. After adjusting the model for age, gender, race, smoking, alcohol, and educational status, the odds ratio still remained significant. There was also a positive correlation with allergy subtypes such as prevalence of rashes, sneezing, and sinus infections with low vitamin D. VDD related to the immune system dysregulation has been extensively reviewed.