Allergic reaction

I think I'm allergic to a drug given to me by a doctor (right...you knew that I was referring to a medicinal drug, right?)
It is highly likely to be either TEMPOL or FEDAC. So I googled Tempol and it's just Paracetamol.. Well I conclude that it's just Paracetamol. I just cannot be bothered to read between the medical terms!
And Fedac, funny enough, is for selesema. Basically it should be a cure for allergies but somehow it causes allergy... but actually, it isn't that odd. I found somebody (online - read her post) who has reaction with Fedac too.

My allergic reaction is mainly skin rashes. ALL OVER MY BODY. Yeah. I pretty much cried that first night. I ate two pills which had drowsiness as a side effect yet I woke up periodically throughout the night to scratch my body T_T Now it's the third day, I'm crying while I leave the shower because I feel like rolling on Durians would be the best backscratcher ever... that's just how bad it is. It's so inflamed - and my face! My face is freaking dry and scaly.
Anyway I paused and thought about why my eczema was flaring up.
Weather? No rain no haze.
Detergents? Unlikely my mum changed her washing detergent
Soap? I'm using the gentlest soap available
NOTHING's ELSE CHANGED....

except for my medication. (I got a fever last Sat, that's why I needed medicine in the first place)

So there you go. I'm allergic to a drug. I wonder how to check for sure?