C.M.
I would suggst an allergy test. You could have a blood draw, but my suggestion is to try and find a NAET practitioner near you. It's a way to treat allergies permanently without any needles. Also, good practitioners can test by muscle response testing. There's a website at www.naet.com. If you're near Indianapolis, we use Trudie Crawford at The Haven Ministries in Camby.
I am actually more allergic to soy than milk. I got traditional allergy treatments from the time I was 3 until I was 21 and I still have allergies. My daughter, who is 5, has also struggled with constant runny nose, cough, congestion, strange rashes and ear infections. I switched her to lactose-free milk and her nose stopped running. Tubes in her ears and adenoid removal stopped the ear infections, but the naet treatments have really helped with the nighttime cough and congestion. I had her on Singulair, but with the naet, she doesn't even need that. I have also had a few treatments and feel better, although I have not been able to get off the Singulair yet. It is a process, just like traditional treatments.
Good luck!