Whoever recites this:

أَعُوذُ بِكَلِمَاتِ اللَّهِ التَّامَّاتِ مِنْ شَرِّ مَا خَلَقَ

I take refuge in Allaah's perfect words from the evil He has created.

'A'oothu bikalimaatil-laahit-taammaati min sharri maa khalaqa.

…three times in the evening will be protected from insect stings.

Ahmad 2/ 290, An-Nasa'i, At-Tirmizi 3/187, Ibn As-Sunni (Hadith no. 68), Ibn Majah 2/266.