Can cats be allergic to catnip?

I put some nip down for the cats. Willy took a big sniff, sneezed a couple of times and then started gagging. I picked him up and took him away from the nip and now he's fine.

Halo, Cammie and Willow enjoyed the nip without any problems.

Can cats be allergic to nip -- or some filler in the nip, maybe?