I would suggest that you do not take any more of Doxycycline.Your rash will probably get worse.
Continue with the Benadryl for another day or two. The rash shold have completely settled by then.
Other side-effects of the drug include the following-
severe headache, dizziness, blurred vision
fever, chills, body aches, flu symptoms
severe blistering, peeling, and red skin rash
urinating less than usual or not at all
pale or yellowed skin, dark colored urine, fever, confusion or weakness.
Stop using doxycycline and call your doctor at once if you have any of these serious side effects.
You could ask your doctor to prescribe an alternative drug.
Thank you Dr. Apama for your timely and helpful suggestions. I did stop taking Doxycycline and will call my GP this afternoon for an alternative. In the mean time, I have continued with Benedryl at 25 mg every 4 hours and will now stretch this out to 6-8 hours through tomorrow; the rash has almost completely cleared up. Thanks again:)