I have been getting allergy shots for 35 years now for environmental allergies. I get both arms, every 3-4 weeks. Right after getting the shots, I get very tired/fatigued. Sometimes I take a short nap. That fatigue lasts for a few hours after receiving the shots. THe next day, I am back to normal. But, if you are experiencing CONTANT fatigue... I don't know. You may want to tell your allergist about that. NOTE: There are a number of things that could be causing your fatigue (including allergies) that have nothing to do with the shots you're receiving.