This topic is a little old now! Sorry, I was too busy at work!!!
Do you have hay fever? (Good) Do you have an allergy to cedar pollen? (Good - but you need 'a')
Also - hay fever is common all over the world, and there are many flowers, grasses and trees which people are allergic to, so 'cedar' might or might not be necessary to say in different situations.
* What is the difference between these?
- Do you have hay fever?
- Do you get hay fever?
Most people think 'get' is 'now', but this is not correct.
'have' is for something that we 'possess' (所有する).
'am' is for something we are. (difficult to change - I am Japanese)
'get' is for something we do not have, but will have in the future. (I want to get a new hat. = I want to buy a new hat.)
So:
- Do you have hay fever? - Great for 'now'. Especially if your friend is showing symptoms (症状)
- Do you get hay fever? - Great for 'ところで' conversations, for example, not is spring. This image is that 'every season' do you get hay fever?
Also:
Are you allergic to pollen? (Great)
Do you have a pollen allergy? (Great)
Are you troubled by hay fever in the spring? (Very good, but difficult!!!)