If my mum is allergic to penicillin what are the chances that i am too?

Not very high: first, you need to have been exposed to something to have an allergy to it. Most likely an 18 yr old has had one of the penicillans, so, exposure, but no history of allergy to it. second, allergy to it doesn't strongly run in families. Third, taking b12 to get more energy when you don't have a deficiency is like adding gas to a car with a half filled tank to make it run faster.

Penicillin allergy: Up to 1/10 people are reported to have Penicillin allergy. Unfortunately it is often over diagnosed, often because of a rash from a viral illness. This underlies the importance of using antibiotics wisely. There is a family history but not enough to avoid the medication. Testing can be done to assess penicillin allergy and there is treatment to help. Chances are you have received Penicillin?