1) How fast did it start—and has it lasted more than 2 weeks? Sudden onset after a new exposure (boarding, swimming spot, grooming product, seasonal change) can point to parasites, contact irritation, or infection risk. Gradual changes that persist >2 weeks deserve a scheduled vet visit, especially if they’re spreading.
2) How severe is the discomfort? If scratching/licking disrupts sleep, causes bleeding, or you see raw skin, treat it as “vet soon.” If your dog can’t settle, is chewing paws constantly, or is painful to touch, escalate.
3) Where is it located? Tail base and rump patterns raise flea concern; paws/ears often track with allergy or yeast/bacterial overgrowth; belly/armpits can reflect contact irritation or infection-prone areas.
4) Any whole-body (systemic) signs? Fever, appetite change, vomiting/diarrhea, weakness, or marked lethargy are vet-now triggers.
5) Are there clues of secondary infection? Worsening redness, swelling, oozing, crusts, a strong sour/yeasty smell, or dark debris in ears suggests you should book promptly and ask whether cytology is needed.