Unlikely to be due to Allegra withdrawal. More like a psychological reaction to withdrawl of Aĺlegra. She can continue Allegra long term too.

Hello there..... I.went through your query.... Many people only need to take an antihistamine when they have symptoms. Unless you are told otherwise, you should stop taking allegra once your symptoms have eased.... Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. ....Consult Physician for further advice....