I have had a severe bacterial infection. I was prescribed ceftriaxone, and when the time came for injecting it the nurse asked me whether I have an allergy to ceftriaxone. I answered that it's my first time, so she did the test and it was negative.
I was expecting a second test because as far as I know from type 1 hypersensitivity the body - even if it is sensitive to an allergen - won't show a reaction the first time. The body makes the particular IgE and in the next exposure of same allergen it will have an allergic reaction.
So why is only one test done, considering the first two columns of the following picture?
From: Harsh Mohan's Pathology textbook 7E