Like CT said, they’re not cones. They’re actually preservatives. As with all things, there is the potential for allergic reactions (whether contact or otherwise), but the vast majority of us use them just fine. I believe most products - unless they’re ‘all natural’ (and even then there are exceptions) - use either isothiazolinones or parabens, and both are known to cause allergies. But I wouldn’t worry about it unless you actually have a reaction.
Cones end in -cone, -conol, and -xane.
