An allergic reaction is an uncommon but possible reaction to any substance or medicine given during any medical or surgical procedure. An allergic reaction would be very uncommon during a vasectomy procedure.
Patients at my center are given either ibuprofen (Motrin) or acetaminophen (Tylenol) before having a vasectomy. Allergic reactions to these medications can occur but are uncommon and are easily treated with an anti-histamine.
Skin hypersensitivity to the alcohol/chlorhexidine solution used before vasectomy can cause temporary burning or itching but these symptoms quickly resolve. Some patients may have skin irritation for several days but this often resolves spontaneously or can easily be treated with over-the-counter hydrocortisone cream.
Latex reactions are possible. We have completely eliminated latex in our office to minimize the risk of latex allergy to our patients.