I was recently prescribed an 8 day course of Doxycycline by my GP...

I was recently prescribed an 8 day course of Doxycycline by my GP for a suspected lung infection (100mg x1 per day). The day after completing the course I started to get spots on my legs and trunk resembling heat bumps which are extremely itchy and after more than a week show no signs of getting better. I have been back to my GP he suspects they are caused by allergic reaction to Doxycycline and has prescribed Chlorphenamine (4x4mg daily) but no improvement yet. Has anybody had similar symtoms and found cure