2. History of previous exposure to poison ivy, oak, or sumac without development of significant contact dermatitis. Significant contact dermatitis is defined as a skin reaction that covered more than 10% of body surface area by the subject's estimation, occurred on the face or genitals, was rated by the subject as moderate or severe, or required treatment with topical, oral, or injectable (systemic) steroids for resolution of symptoms. History of exposure will be documented using the Allergic Contact Dermatitis Questionnaire (Appendix 1).