Not a provider but I'll give you my two cents for free, not that it's worth even that much.

I've never been asked if I had an allergy. I don't have any. Hypothetically, if I had a latex allergy and I failed to mention it at some point before the condom went on and I had some form of reaction, I would consider that 100% my own damn fault. If a person has any kind of allergy and they know about it and they're over 16 years old, it's their job to take care of themselves and avoid their allergens. Not the world's job.

If someone was going to ask me, frank and honest, quick and simple would be my preference. Don't pussyfoot around, just ask no big deal.

it turns out that Skyn condoms are latex-free. (Thanks Google!) I just like them because they feel great!
I've never been asked about a latex allergy. I suppose that if I had one, I'd bring along an unopened box of latex-free condoms.  
Sorry, that still doesn't answer your question, though ... Maybe you could sexily offer a choice?

Don't have to ask cute analogy or dance around the subject. Ask like an adult and they will appreciate and find that sexy. Always awesome to have options !

...I always mention them in communication with my provider BEFORE our session. Certain scents, burning candles (particulates and more scents), some cleaning products, etc., can be a trigger for an asthma attack. So as the person with the sensitivities, I feel it's incumbent upon ME to make sure an allergic reaction doesn't get in the way of a great time.

I'd appreciate the inquiry from someone concerned about an allergy to latex and the straightforward way is sexy -- but I value clear communication.

GFE $$$ / hr
Extras:  
Greek +$
Couples +$
MFM +$
EpiPen +$$$$ (free delivery)
Two EpiPens +$$$$$$$ (free delivery plus 911 call included)

They are just better condoms overall anyways...However I would assume a hobbyist would know he is allergic to latex prior to the meeting and communicate that in a discreet way or bring his own.