Possible salmon allergy? does it apply to all fish?

No: No, get a fish allergy panel drawn or see allergist.

Generally not: Allergies to both fish and shellfish are most often very specific; you can be allergic to one species and not to any others. If the allergy is mild (e.g., a little itching in the mouth when you eat it), you can safely (but cautiously) try other fish. But if you had a serious or life-threatening reaction to one kind of fish or shellfish, it is best to get tested by an allergist before trying others.