Experts,<br/><br/>If you want say that you have a particular kind of allergy, such as in the following,is the "a-particle" necessary or not needed?<br/><br/>I have (a) pollen allergy.<br/>I have (a) cat allergy.<br/>I have (an) egg allergy.<br/>I have (a) wheat allergy.<br/><br/>If both can be used, which(with a or without a) is considered to be more common in everyday usage?<br/><br/>Thank you so very much.