Is it an allergy to dogs or food or pollen?

[mjk]

My stepson visits every other weekend. He is 7 and often has a bad cough. He has been treated with Albuteral for croup a couple times in the past 2 yrs. Years ago, he was tested and among his allergies was a reaction to cats. So when he is visiting our dog stays outside. Many times when we pick him up after not being around him for 2 weeks he already has a cough. If he eats junk food he gets very phlemy and coughs. His mom feels he has an allergy to our dog. Last time he went home on Sunday and was taken to the doctor on Thursday with the cough she said was caused by exposure to our dog. If it was from the dog, would his symptom be a croupy sounding cough and would it last for several days after he leaves? I think he has food and seasonal allergies. He is overweight and doesn't go outside much until he visits us and pollen was over 2000 on his last visit. Now she doesn’t want him to visit because of the dog. She has been reluctant to let him visit his dad since I came along.