Go to a friend or family member's house where you know a cat is living and get the child to interact with the cat. This way, you can watch for signs of a cat allergy.  Be aware that cat allergies can arise from contact with the skin, fur, dander, saliva and urine of the animal. It is important to note here that you should not try exposing your child to cats, or any animals, without knowing if they do or don’t have an allergy  if your child suffers from asthma. Simple allergic symptoms can trigger potentially deadly asthma episodes. If your child shows any of the following symptoms, he may be allergic to cats:  Excessive coughing, wheezing or sneezing Gets hives or a rash on the chest and face Has red or itchy eyes Redness on a spot of skin where the child was scratched, bitten, or licked If your child complains about any of the following symptoms while exposed to the cat, your child may have a cat allergy:  Itchy eyes A stuffy, itchy, or runny nose Itchy skin or hives where the cat touched the child If you do notice any of the above symptoms in your child, it is important to remove her from contact with the cat until you have devised a plan to lessen or eliminate the symptoms of her allergies. Observational and anecdotal evidence may be enough to determine a cat allergy in a child. However, you will want to visit the doctor and get an allergy test. Keep in mind, though, they aren't always accurate, so if your child tests negative, you should still observe the child for signs of allergies when he is exposed to a cat. Most allergic reactions are limited to redness, itching, hives and nose stuffiness, but signs of more severe allergic reactions may become apparent when exposing your child to a cat. Swelling of the throat can occur in severe allergic reactions, which can lead to the constriction of airways. If this happens, get your child to a medical professional immediately and do not expose them to any more cats in the future.

TL;DR in Vietnamese:
Tạm thời cho trẻ ở gần mèo. Quan sát trẻ. Lắng nghe trẻ. Tách trẻ khỏi mèo. Cho trẻ xét nghiệm dị ứng. Phát hiện dị ứng nghiêm trọng.