I get bites all year round that itch and very often get infected to the extend that I have to have antibiotics. Anything and everything bite me. I have had tests for years by a Dermatologist and we have been through the following reasons
Cat's flees (we got rid of the cats, still got bites)
Dye in tights (washed all tights before wearing, still bites)
Citrus fruits (stopped for 3 months still got bites)
Ants, flies, bed bugs, or any other creepy crawly Betnovate recommended at night and masses of moisturiser in the day. This definitely helps, but still bites.
Sun reaction, same cure as above and plenty of sun protection, still bites)
I now get prescribed a 5 days course of prednisolone when I am really bad, which clears them up at the time, but then it starts all over again.
Stop scratching only cure but almost impossible and I also use an antihistamine cream and Calamine lotions on new bites, which helps. I cover bad ones up with plasters so I cannot scratch at night.
Hope any of this might help