hi pregnancy basically causes increase in all cell types to increase ur blood to suppy extra for the baby. in the process eosinophils blood cells responsible for allergy also are produced in excess. a little trigger like perfume, dust or even steam might cause release of allergy chemicals from these eosinophils. u can use oral antihistamines like tab chlorphenaramine, but side effect of that is being drowsy. and if its severe asthama and u have had deriphyllin shots earlier uneventfully, no contraindication to that is there in pregnancy either. u can take those shots in severe conditions. but use caution and no drug is to be over used in pregnancy. i woud like to suggest other simple measures like, cold water baths, avoiding air freshner/ perfume/deodrants, avoid any allergenic foods like nuts, stay away from dust. by 4 th or 5 th month ur asthama ll have come down. thats when eosinophil count reduces.. hope it helps