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An alternative strategy , exploiting breakthroughs in understanding the molecular basis of allergenicity and the key role of innate immune mechanisms in asthma , is to direct new approaches to the disease triggers themselves : allergens .
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Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None