What Causes Red Itchy Bumps That Look Like Insect Bite?

Greetings, I have big red itchy bumps thats looks like bite for the past 4 weeks, since i thought they could be bites i had an exterminator come in and look if there was anything biting me in the house, they found nothing and confirmed it was nothing related to insects, is there anything else that could be making me have a bite reaction? Thanks in advance