1. Allergy and Clinical Immunology Service, Division of Internal Medicine, The "Dr. Juan I. Menchaca" Civil Hospital of Guadalajara, University of Guadalajara, Guadalajara, Jalisco 44340, Mexico.
2. The Hospital Regional of Ciudad Guzman, Ministry of Health, Ciudad Guzman, Jalisco 49120, Mexico.
3. Medical Intern, Southern Region University Center, University of Guadalajara, Ciudad Guzman, Jalisco 49000, Mexico.
4. The Public Health Institute, University of Veracruz, Xalapa, Veracruz 91190, Mexico.