continuing coughing

[shank]

my sister has had a severe cough for the past couple of years which has made her quality of life poor because it eventualy ends up making her sick and she has to leave shops ect, she has been to doctors ,hospitals and they say it is an allergy or they give her nasael sprays 'she sometimes gets a couple of weeks and it will ease off at the moment it is very severe and is getting her down.

[Mike VG]

Has she had a professional allergy test? TB test?
Mike VG