What are allergy test like?

I had two allergy tests at two different times and at two different clinics. They were both done the same.Your naked back will be exposed and someone will insert about 20 +/- needles into your back. The needles will contain an allergen. If slight swelling occurs at the site of any needle you are allergic to the allergen on that particular needle. Don't worry the needles are only inserted under the skin. Not painless but only slightly so. Hope this helps.