I have been taking Solar sublingual b12 alternating between 5000 mcg and 2500 mcg for about 6 weeks. This morning I woke up with an itchy back covered in red spots. I also have them on my arms, neck, face and a few on my front. Is it possible to get a reaction to the B12 medication after 6 weeks.? Is my b12 too high? I am having my first 3 monthly injection tomorrow. Never had anything like this before. I am also taking vitamin d. The pharmacist said it looked like an allergic reaction and suggested antihistamines which I have been taking. I am still itching.