Could this be soy allergy?

Here is my situation: few days ago I had soy vanilla-flavored milk that I do not normally take. Less than an hour after that I noticed I had  some trouble with swallowing and approximately 10 minutes later I started feeling pressure in my throat. I didn't have trouble breathing but my airways felt somewhat constricted. The feeling of constricted throat lasted for a day and half. Next day I woke up with post-nasal drip. The thing is that, as I mentioned above, I do not normally have soy milk. I only had it on 2 other occasions. The week before I also had vanilla soy milk (different manufacturer) in the evening and woke up with the exact same feeling of tight throat, that, again lasted for few days. It was followed with post-nasal drip like this time. At this point you would normally suspect soy allergy, but there are few things that just don't fit in. I  had chocolate- flavored soy milk maybe a month ago (in fact, that was my first time to try it) with no reaction whatsoever. I also thought that it might be vanilla that is causing the issues but I had other vanilla-flavored drinks and products all my life and never had anything similar to this. Another thing worth mentioning is that I had some cold-related problems during this period. Sore throat on few occasions during 2 week period. At the time I took soy milk I was symptom- free, however. At first I thought my symptoms were cold related and I went to see the doctor and voiced my concerns. She said it was sinus infection and  put me on antibiotics and post-nasal drip did disappear (could be coincidence) but it came back today. I have been taking antibiotics for  4 days now (2 more days to go) and this morning post-nasal drip resurfaced after 4 days of absence and 2 days since last having soy milk. So, my question is are these even  symptoms of food allergy? If they are, would they last for so long after the exposure? The first time everything lasted for at least 7 days (there was no overlap though; 3 days of tight throat and then 4 days of post-nasal drip). I've never had problems of this sort, yet I'm sure I must have had soy before in some form( since it is commonly found in number of processed foods). Also, the first time I didn't have any problems in first couple of hours, only the next morning did the symptoms appear (although I did consume it in the evening). Do you think this is infection of some sort and the fact that my symptoms are preceded by soy-milk consumption is only a coincidence? I know this is really long, but I would be extremely grateful if somebody would give me his/her opinion. Thanks in advance.

[sprinkles77]

Both of my booys have either food or enviromental allergies.  This sounds sinus related to me.  However my oldes son, 15, gelot sinus infections more often than most people we took him to an allergist and foundout he is allergic to so  many things, grasses, all tree pollen, ragweed, animal dander, mold, and dust mites.    You can take a zyrtech at night with benadryll during day to help dry up sinuses.  Try it at night to see hiw sleepy they make you and your body produces more histamines at night so an antihistamine is very helpful.    Changing his pillows every 6 months helps too due to dust mites.  As well as a hypo allergenic bed wrap.
1) Have you bern allergy tested within 5 years. My son went from cat only allergens to everything in the 5 year gap.  You can do at RAST test at your doctors office they draw blood you will get the results in two weeks or less and usually this test will fall under all insurances it is very common.  If you prefer an allergist and immediate results you can have the scratch test done.   And should fall under your specslist copay.  Either way take no antihistmaines for 72 hours to get accurate results.  I would reccomend testing of some sort. Once DS knew about his allergies he was able to take meds as a daily  preventative and he was not miserable got fewer sinus infections, and missed less school.  
2) If it were food allergen it would probably be more common soy is in most everything: cereal, cookies, chips, breads.  But you can be tested for this also during either of above tests they will do all major food and enviromental allergen groups.

[ChitChatNine]

Just wanted to welcome you to our food allergies community.  I think the above poster has given great info!

C~

[beakeradams]

They say that 70% of our Soy products comes from Monsantos round up soy seeds.  They had this brilliant idea to make the soy bean plant survive a round up treatment so that they could still get rid of the weeds but be able to harvest.  It might be possible that those other times you didn't have any problem was because they weren't from round up seeds.