What Causes Itchy Rashes In The Thighs,legs,feet And Arms?

23 y/o male medical student, I moved to a Caribbean island 6 months ago and I have been getting very itchy late at night only when I am at home (usually at this time it becomes very humid and warm), sometimes I get hive like appearance but often I just get very itchy and a slight rash develops (may be from itching) on my thighs, legs, feet and arms. I have no history of allergies or any other diseases.