I get those symptoms. I've had them for the past 20 yrs - went to the doctors who told me I had an allergic reaction to something, and assured me I would find out what it was by process of elimination.
Thought it must be something I could smell, so I did the process of elimination thing with things like perfume etc, but was baffled.
A couple of years ago, after being sick to death of having flu like symptoms every other month, somebody recommended an 'Allergy Testing Service'.
The test included allergy testing, food intolerance, a vitamin analysis and mineral testing. Oh my god! It was the best thing I had ever done - so disappointed my doctor didn't recommend this testing after visiting him for the umpteenth time - but he said he wouldn't recommend as the testing I had was classed as alternative medicine.
The test was non-invasive whereby a metal rod was rubbed against the finger. The rod was attached to a machine that was fitted with over 100 food and chemical products. You're tested for sensitivity to items such as grass, dust mites, all milk proteins, eggs, fish, fruits, dairy etc. Your tested also for vitamin deficiencies.
I know I suffer with low iron, so when the test showed this I wasn't surprised.
However I was surprised to learn that I was highly sensitive to Cow's milk and Monosodium Glutamate (E621).
As soon as I cut these things out of my diet - what a difference.
I still get caught out - I had some monster munch yesterday which contain the Monosodium Glutamate (E621) and I feel fluey today. But at least I know what caused it.
Basically if you're allergic to something, itchy nose, fullness in ears, sneezing loads and a headache all over are a good sign that your body is trying to get rid of whatever it doesn't like.
My test cost £45. The doctor visits many health centres to carry out testing. Not sure where you're from. I'm from the northwest - if you're interested to see if the doctor does testing in your area he can be contacted on 0151 652 4277. My doctor was Alan Hopewell.
Hope this helps.