You can be born allergic to anything.
Yes, people frequently become allergic to nickel and chromium (though you are unlikely to become allergic to gold or platinum). To check this it is possible to have an allergy test.
it depends on the age and breed.
yes
6 and up but if ur allergic dont get a rat
Something can become swollen from an allergic reaction.
People are allergic to all different kinds of things, there is no real way of telling why or how, they just are. I, for example, am allergic to 14 things, some of them I developed with age, some I was born with.
Borrow one for a week and find out. People allergic to one kind of regular dog are not necessarily allergic to others. For example, I work with sable German Shepherd Dogs whose fathers are from the former Chez. Republic and moms are from Germany. Many people allergic to American German Shepherds are not allergic to these. But, some are. Remember too that your system changes with age. What you were once allergic to, after time, you may no longer be, and things you weren't allergic to, may become a catalyst for reaction. Also, their are breeds that many react less to, or not at all. Google 'em.
Skin
Milk Actually they are allergic to avocado and rhubarb!
Some glitter contains the mineral mica. Some people, such as myself, are allergic to mica. I can break out into hives or at the very least become very itchy when exposed to glitter with mica
You have become allergic to the material that your ring is made of.
Maybe, but not a very good chance. Probably about 10% or 15%