Is method of administration a factor in drug allergy?

Oral vs iv. In some patients with allergy to drugs, giving orally might not trigger and allergic reacton, while givne intravenously it does. This has been reported with amoxicillin. It appears that concetration is importnat, and in some case, metabolism. Without challenging, it is not easy to predict a reaction in a particlar individual. Safest is always to avoid the drug entirely.