Suggest Remedy For Welt On Skin

Please help. I currently have what I thought was a hive or welt that starts out oval(ish) or teardrop like that's a bit itchy not always at the beginning. It then charges shape over a matter of hours, it's later stages are that it quadruples in size and becomes very hard. At this point it begins to get a head and expells a liquid that I think is cloudy. At the moment it's very very itchy in its late stage So far I've had this happen three times in a month. Any ideas?