Q.Ligustrum ovalifium
Hi there. My partner came home the other day with lumps on his arm and hand after brushing against a ligustrum hedge. He said it was a sap like substance that got on his skin. My question is this: is it a common reaction or does he have an allergy to the plant himself. Also despite washing sap off he touched his mouth with that hand (lump had leaked puss) and now he has a lump on his lower lip, he’s worried its contagious. Is it?

Privet berries are poisonous for dogs as well as humans and the leaves can be even more toxic in large quantities. Toxicity is due to the presence of terpenoid glycosides.
You can call Poison Control to see if they have any toxicity info on plant contact.