Unfortunately, many new allergies start with no previous symptoms and you can develop them at any age. The best way to know if the allergy is from cats /dogs is to either get tested or to avoid any contacts with the cat/dog and see if the condition improves.
I kept rats for years with no problems then about 6 years ago I started to become allergic and after two years of suffering finally relented and gave them up. The only way as Ani says to diagnose an allergy is to get properly tested. If your son proves to be postive towards your pets, understandably giving them could be very painful emotionally towards him and the rest of the family. Should your son have a positive reaction to animal dander, don't immediately think the animals have got to go. I am allergic to animals and yes the Ratties did have to go but I still enjoy a rewarding relationship with my dog despite critiscism from certain medics. Sometimes the emotional benefits can outway the physical syptoms. But there is much you can do to hel-p your son if he is allergic, like keeping animals out of bedrooms, getting rid of carpets where animal hair can be difficult to remove etc. Finally there is a website called the healthy house limited, they sell a product that can be sprayed onto animals that can dampen down the allergic reaction. I can not personally recommend it because I have never tried it. But the no carpets and regular house cleaning helps me.
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