Suggest Treatment For Skin Allergy

Hello Doctor. My query is regarding my mother. She is suffering from allergy since a long time. Its like when so ever she moves from a place/room with lower temperature to higher temperature or visa versa she gets itching all over her body and after some time where all she starches over her body she gets reddish rashes. She is taking cetirizine medicine for the same since last 2-3 years but its an temporary measure. Please provide assistant for permanent solution to this problem.