The benefit of Patch Testing with Ultrasonic Bath Extracts in Special Cases.- How to Manage Occupational Contact dermatitis.- Patch Testing and Atopic Dermatitis.- Pitfalls.- Legal Aspects.- Updating semi-open tests.- Patch Testing.- Do’s and Dont’s in Patch Testing.- Prick Testing.- When Patch Tests are Negative.- Patch testing validity.- Assessment of the Clinical Relevance.- How to Select Extra-Allergens – or Problematic Allergens.- Patch Testing in the Tropics.- Making a Diagnosis.