a few people have said titanium isn’t usually fortified with nickel so I’ll look into that.

It isn't. I love titanium (no allergy though). I am wearing a titanium watch now.

If you can, try to handle the watch before you buy. Citizen has several titanium models frequently found in stores. They say "titanium" on the dial.

However, I am personally unaware of what the casebacks and clasps may be. You'll have to investigate that. Also note that some watch designs, including a few of the Citizen titanium watches, don't allow for pass through straps, so you should also consider that detail should you want to replace the bracelet they came with.

The Citizen Promaster Tough watches don't have casebacks, and they are steel, however, they may have a titanium coating on the outside.

If you can determine if a watch is a problem by handling it in person, that would be useful.

• Promaster Tough
• Promaster Tough Black (likely has even more coatings to protect you from direct contact with the metal)
• Promaster Diver Titanium (if you can wear this, it is a fantastic watch, very light and thin and exceptionally good and it looks like the caseback is also titanium, but it is hard to see on the site.

These watches allow for passthrough straps.

Bertucci, Boldr, and others have more basic titanium watches, but I do not know their casebacks.