Is it possible to be allergic to levothyroxine? I have had reactions to Synthroid & all of its generics. Tried tirosint but am allergic to the gelatin

Possible. It is possible to be allergic to anything, just as you are allergic to peanuts and wheat; however, the extent of allergic reaction is what matters. If it is tolerable and something like just mild, u can take it and just bear with it. If it gives you shortness of breath or hives, etc then do not take it at all. Talk to your primary care physician about options.
There is no. Allergy to the active ingredient, which his been in your body since you were in your mother's womb. A rare person is sensitive to some of the fillers and coloring agents. The yellow die (which has since been changed) in the 100 micro gram pills were the most common. The 50 microgram pills are white with no coloring agents. You can take multiples of them to total dose and usually have no problem.