allergy Vs. Allergies

[High on grammar]

Dear English teacher:
I have a question about the word “allergy”: Should it always be used in the plural form? For instance, can I say, “My allergy is getting worst” or should it always be “my allergies are getting worse”? What if I was referring to only one case?
I have heard people say “allergies?”(Always plural) when someone sneezes.

Except when it is used before a noun like, allergy season, food allergy and the like.
Thanks

[Gillnetter]

Dear English teacher:
I have a question about the word “allergy”: Should it always be used in the plural form? For instance, can I say, “My allergy is getting worst” or should it always be “my allergies are getting worse”? What if I was referring to only one case?
I have heard people say “allergies?”(Always plural) when someone sneezes. I suppose that they are asking if the person sneezing has some allergies. I haven't heard this before but it is likely. I would be just as likely to say, "Do you have an allergy?",or, "allergy?".

Except when it is used before a noun like, allergy season, food allergy and the like.
Thanks

A person can have an allergy just as a person can have a car. A person may have allergies and a person may have many cars.

[SoothingDave]

If you have a known specific allergy, you would proabaly refer to it in the singular. "I have a peanut allergy."

People who sneeze a lot usually are sensitive to various environmental factors, so it is usual for them to say they have allergies.

[High on grammar]

Dear English teacher:
I have a question about the word “allergy”: Should it always be used in the plural form? For instance, can I say, “My allergy is getting worst” or should it always be “my allergies are getting worse”? What if I was referring to only one case?
I have heard people say “allergies?”(Always plural) when someone sneezes.

Except when it is used before a noun like, allergy season, food allergy and the like.
Thanks

Thanks