As a child i became allergic to amoxicillin, i took it as an adult and nothing happened, why? is it possible to grow out of being allergic?

This : This is very common. A child is thought to be allergic to a drug (commonly amoxicillin) this is usually because the child's mother or guardian incorrectly identifies a symptom a child has while taking antibiotics and assumes they are allergic. For example, a patient's mother told me her child was allergic to amoxicillin.I asked why, and she stated it was because he had a stomach ache after taking it. This did not indicate an allergy, but the mother thought it did. Allergy to medication usually presents as an itchy rash, hives, and more seriously difficulty breathing. In your case it is likely that you never had an allergy to amoxicillin.

Yes, but...: You were probably never allergic. The infection for which you were being treated probably caused the rash - lots of viral and bacterial infections can be associated with rash, especially in children. It is always important to write down as much detail as possible about a possible drug reaction, and get evaluated by an allergist to determine whether the reaction was truly related to the drug.