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If You have not already got a blood TC and DC done, you should get it done, just to exclude Tropical eosinophilia
If dust allergy
is the cause you may consult a specialist in asthma
, who may be having a kit to test for allergies due to various causes. They inject small quantity of various allergens subcutaneously and watch for reaction. Once they identify the allergy causing allergens, they can treat you accordingly.