A 13-year-old boy stung by a wasp had to be airlifted to Waikato Hospital after having a severe allergic reaction today.

The Waikato Westpac Rescue Helicopter was called to a farm near Hinuera, south of Matamata, at 1.30pm today when the boy had an anaphylactic reaction to the sting.

A St John Ambulance paramedic stabilised the boy at the scene before he was flown to Waikato Hospital for urgent treatment.

Anaphylaxis is a serious allergic reaction that can cause an itchy rash, throat swelling, low blood pressure and death.