Allergies or illness?

Dr
My three year old woke up with snot constantly dripping down her face and lots of sneezing, she has watery eyes and we just had our half acre land mowed the day before, I left the windows open to cool off the house not realizing it might trigger a reaction. My first thought was allergies, but now she's developed a fever of 100.5. Does this still sound like allergies or definitely illness? 
She seems tired, cuddley, but not sleeping or anything. her appetite isn't non existent but it's definitely not what it usually is.