Hi, welcome to the forum, there are no such reports available regarding allergy shots inducing HSV-2 outbreak. Allergy shots are unlikely to cause HSV-2 infection. Although the known risk factors are Female gender, at least Six years of sexual experience, History of a partner with oral ulcers and Prior history of STD. I hope this helped you.
Herpes simplex 2 virus s known to cause Genital herpes. The symptoms depend on immune status of a person which ranges from no symptoms to multiple painful herpes vesicles. In such cases appropriate treatment with ant- viral is necessary. If one's immunity at any instance comes down there are chances of flare up. Hence, one need to have nutritious food, regular exercise etc. Take care and regards.
I assume that you are talking about a herpes simplex virus - 2 out break.
I would say probably not, but sometimes stress can cause any herpes virus to act up and allergy shots can cause some amount of stress on the system.
He should really discus this with his doctor though.