Why do we develop allergies to rats after working with them?

well maybe they have bacteria...maybe they have fleas...maybe they ate somthing wrong?or maybe ur prone to that?

That is a very neat question, because it really is something to be concerned about when you work with rats.

One study found that 23% of those who work with lab animals were allergic to their charges. Rabbits caused the majority of the respiratory symptoms, while rats caused most of the skin reactions. Guinea pigs and mice also caused allergies. Another study found that allergies to mice and rats developed in 10-30% of laboratory animal handlers.

Of course, lab workers are exposed to larger numbers of animals than the typical rat owner, so I don’t think allergies to rats are that common among rat owners. But it is common for a person to get a skin rash after handling rats. Their toenails are so sharp, they actually penetrate the skin without the handler knowing it. This opens the skin to allergens the rat may be carrying on its feet

Rats produce three types of allergens: dander (dead skin cells), saliva and urine. (Contrary to popular belief, animal fur does not cause allergies.) When rats groom themselves, their saliva is spread on their skin and fur. They can also pick up urine on their feet or other parts of their body. As these allergens dry and flake off, they can become airborne.