Red glow symptoms and conditions

I have been on Singular for the past three years. I usually take a tablet in the evening at the same time I take a baby aspirin and Nyaspan (cholesterol). I didn't seem to have any problems except waking up periodically throughout the evening; thought this was due to age (63). I was without my Singular for about 10 days and then got a new prescription filled. When I took the first tablet I went to sleep and was awakened by a "burning, prickly" sensation im my arms, chest, face and thighs. I went into the bathroom and found myself covered with what I would call hives. I felt hot. Thank heaven I had some liquid Benadryl. After about 30 minutes I finally could relax enough to get back to sleep. By the next morning all that was left was a slight red "glow"; could have thought I went for a tanning session. The pharmacist couldn't give me an answer; I am now waiting for my doctor's input. In the meantime...I'll skip the Singular. (next time it may affect my breathing)