The main reason why your allergies could be making you tired is because they can get worse at night, making it challenging to get a good night’s rest. A stuffy nose, pounding headache, and relentless coughing are a recipe for disrupted sleep.Additionally, the histamines that your cells release in response to an allergen can also exacerbate tiredness because your body is working hard to block a harmful substance. The allergy fatigue you experience is similar to the exhaustion you feel when you have a cold or flu. Falling sick can be draining enough, but when your body works overtime to ward off the viruses and bacteria, it can often leave you feeling worse for wear.