Your body, even as "male" is already producing some E so I doubt you'd be allergic to E; after all, it's native to our bodies and our bodies have been producing it for millions of years. You could be allergic to higher levels in the sense that you are not ready for transition but that is a totally another thing. On the other hand, since Spiro will be newly introduced in your body, you might or might not react adversely although usually, it is well tolerated under the supervision of a doctor. Lastly, you could be allergic to inactive, non medicinal ingredients included in preparation like coloring (dye), preservatives, alcohol, oil, etc.
