Hello I Have Cats At Home But Recently Got A

Hello i have cats at home but recently got a boy kitten my 7 year old son would play with the kitten at times then I notice he would start coughing having cold for weeks then he got a small lump at the left side of neck under the skin you can feel it if you touch it. When the car goes in the car litter box and do their thing the dust from cat litter raises and get into the car fur then when my son play with cat he sniff the cat he then cough or have a cold i really study this on many occasions that my believe and what I see now we are thinking to take him to children hospital Boston either we have give the cats away what do you think of this situation?