Good morning, ma'am,
If you suspect a cold allergy, I see no problem in trying Reactine. It is recommended to give it at least 1 hour before exposure to cold, maximum 1 time per day. Your pharmacist will be able to confirm the volume of solution to give her and will keep a record of it, which will allow close follow-up with you and her.
Do not neglect non-pharmacological measures
An ointment or cream should be applied to the skin before discharge to protect. I suggest a fragrance-free product ideally like Aveeno, Glaxal Base, Eucerin among others.
It's time for toques, scarves or neck warmers and gloves, even when it doesn't seem to be very cold. The current weather and wind are quite irritating for the skin
Finally, when going out for long periods of time, I always suggest applying sunscreen, even on cloudy days or in winter.
I hope I've been of some help to you, and I remain available if you have any further questions
Tom Samaha, pharmacist