hi..thanks for the query..
The symptoms you mention seem to be a part of a disorder known as URTICARIA
. this is manifested either for few days or months to years depending upon the severity. Altough it is not something that you should be very worried about, it runs a prolonged course of exacerbations and remissions in most cases. i suggest you go ahead with a course of oral anti histaminic medicines which are available OTC in most countries.If it is persistent over 6-8 weeks ,you might require a blood test
to be done.
Observe your daily routine carefully..some people do see the lesions after stress
,having particular food, on exposure to a particular oral/inhaation/topical agent etc.