> In your specific case, you might want to consider
> Allergra tablets, which are lactose-free.
>

Be careful:  depending on which Allegra you get.  Some are NOT
lactose-free (as I found out to my dismay).

You can always ask the pharmacist to look at the package insert
(or better yet:  ask them to give it to you, which most will do without
argument (at least in my experience)) and tell you if there are any
inactive ingredients which may be a problem.  If so, ask if there are
any alternatives without lactose or whatever the problems is:  and if
there are no direct alternatives/generics he/she may be able to suggest
similar products and contact the doctor on your behalf.

In any case, assume that even the smallest amounts in the pharmaceuticals
are enough to cause problems.