What Causes Contact Urticaria?

My Name is Sivakumar aged 43, height 178cms and weight 81 kg. I am occasionally having acute itching in my palms and feet and the palm and feet become reddish in some parts. I consulted a doctor and he diagnosed it as contact urticaria. What is the reason for this occuring occasionally. Whether is it due to some food products or due to dust allergy. Is there any medication for curing this permanently.