Avoid spicy, oily food, mushrooms, brinjal, potatoes, tamarind, black pepper, non veg once in a week, consult near by Ayurvedic doctors

Ayurveda medicines like haridra khanda, laghu sootha shekar  ras, histantin tab, sarasaparilla etc help in controlling allergy. Chronic cases panchakarma treatments like dhara,  vamana, virechana helps along with meducines

In ayurveda it is called as Shitpitt. Vitiated pitta when comes in contact with cold, it induces itching. If it is for such a long period, I think u should go for Panchakarma- Virechan. Meanwhile u can take medicines - Haridrakhand granules 2tsf with lukeworm milk or water. Add kokum to ur diet. Consult nearby Ayurvedic  doctor for proper treatment.

Try wearing full sleeves clothes. Also you should apply a moisturiser on face and neck. Eat good amount of fruits and vegetables. Increase your immunity by taking Chawanprash daily.