Hi arthur,
It would be very uncommon because most latex “allergies” are contact allergies and there is no contact with the latex in a mattress and foamed latex is also very different from the rubber used in gloves and other products that are a common source of latex allergy issues but a “true” latex allergy is also possible in which case all natural latex products should be avoided (most people that have a “true” or type 1 latex allergy would also need to carry an epipen because latex exposure can be very common in our society). There is more about latex allergies in post #2 here.
Phoenix