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The aim of this study is to show the transferability of the two - tiered approach with training chemicals : 3 sensitizers ( DNCB , resorcinol , pPD ) and 1 non sensitizer ( lactic acid ) in tier 1 and 2 sensitizers with different potency in tier 2 ( DNCB ; extreme and resorcinol ; moderate ) .
 DNCB, resorcinol, pPD, lactic acid, DNCB, resorcinol
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 DNCB, resorcinol, pPD, lactic acid, DNCB, resorcinol