it is very likely that your skin reactions are the result of changing your laundry soap. unfortunately when your skin becomes sensitized it takes it a while to settle back down. unfortunately this is more difficult in the winter months because your skin suffers from the temperature extremes of this time of year making a usually small problem bigger than it usually would be. taking an antihistamine to help minimize the irritation is a good idea just be careful about the drowsiness that can occur. you might also consider using a little bit of hydrocortisone cream for any areas that are especially inflamed. aveeno baths can help soothe irritated skin as well.
my skin started itching after using a new detergent. i am taking an antihistamine to relieve it. what more can i do?