i love coffe -“What’s the difference between being allergic and getting infected? Doesn’t being allergic to nickel make the area infected?”
An allergy to something that touches your skin can cause “contact dermatitis”. An infection is caused by micro-organisms invading the area. This can be viruses, bacteria, fungi or other organisms. So no, an allergy to nickle doesn’t make the area infected. And it is possible to have one on top of the other. This is usually called a secondary bacterial infection. But it can work the other way around, eg.- the area is infected and you put on an antibiotic cream/ointment – you can have an allergic reaction to the stuff that is supposed to make the infection better. A medical professional with a trained eye can usually tell the difference. If the professional is in doubt, they can do a gram stain and/or a culture and sensitivity to look for bacteria.
Bacterial infections are treated with antibiotics, whether topical or oral. Allergic Dermatitis is treated with antihistamines, astringents (Eg. Domeboro solution) and steroids(either oral or topical).
This is why I said to go see you PCP for diagnosis and treatment.