If you can completely avoid the things to which you are allergic, you cannot experience an allergic reaction. But completely avoiding your allergens is usually easier said than done.
For instance, if your lips swell and your throat itches when you eat shrimp, you probably choose to avoid it. And if you think you’re allergic to penicillin, you would tell your doctor to not prescribe it for you. But the things that cause most allergies are submicroscopic components of invisible inhaled particles, so they’re pretty hard to avoid.
There are multiple “partial avoidance” measures you can do to at least reduce, if not completely avoid, inhaled allergens. Partially avoiding or minimizing exposure to allergens might be as easy as not letting the dog in your bedroom, or wearing a special paper mask that filters out dust and pollen when gardening or sweeping out the garage.