A reaction to summer fruit sap
A chemical in the sap called urushiol causes a delayed skin reaction 12–24 hours later. This can take the form of an itchy dermatitis, blisters in a linear distribution of the dripping sap or hives.
Urushiol is also found in the peel and in the leaves but not in the fruit itself or the juice. If the skin comes into contact with the sap, wash it off with dish washing liquid as this is more effective in removing the oily sap.
A florid reaction may need a short course of oral steroids.