You are absolutely right in thinking these are 'hives' and in medical terms, the itchy red skin lesions that last for a few hours is called urticaria
You can also get contact urticaria if there is pet hair on the bed, setee (sofa) etc [if you have a cat] and pressure urticaria due to tight clothing.
is fine as long as you dont get recurrence or breaking out with 'hives' everyday, at which point you will need long-acting antihistamines like fexofenadine
If this is occuring for more than 6 weeks, you will need antihistamines for a period of 3 months without a single recurrence.
Hope this helps.