Is it an allergy?

[MoRaw]

My son has a suspected diary allergy since he was born. He was put on and lately Aptamil Peptid.

However, he has never been tested for allergy.

I began giving him diary products when he was about 8 months. However, for the past few weeks, he has been suffering from nasal congestion and phlegm particularly at nights. I am wondering whether it is because of the introduction of diary. This did not begin immediately after trialling diary products but I notice that it has been about 4-5 weeks and he has nasal congestion and phlegm in the throat that simply won't go away. I should note that he had a cold about 5 weeks ago.

Do you think this is an allergy response or perhaps he is still recovering from the cold 5 weeks on?

I could be either. Annoyingly!

My eldest has had a cold for nearly two months now. Colds are rife.

Yet Ive heard a few times about dairy being reintroduced and after a while the body responds with congestion (and often wheezing). It'll likely get worse if it is that.

I guess the only way to tell is take it off him again for a few weeks.

What were his orginal allergic symptoms?
How old is he now?

Tbh testing wont always be clear.

My baby recently had a result come back to say he was highly allergic to soya. Yet ate soya the day of the test and was fine.