Common signs of illness in dogs can vary depending on the condition, but some general symptoms to watch for include:
1. **Changes in Appetite or Thirst**: Sudden weight loss or gain, increased or decreased appetite, or excessive thirst.
2. **Vomiting or Diarrhea**: Persistent or severe vomiting or diarrhea.
3. **Lethargy or Weakness**: Unusual tiredness or lack of energy.
4. **Changes in Behavior**: Aggression, anxiety, or withdrawal from interaction.
5. **Skin Issues**: Excessive itching, redness, or sores.
6. **Respiratory Problems**: Coughing, wheezing, or difficulty breathing.
7. **Urinary Issues**: Difficulty urinating, blood in urine, or increased frequency.
8. **Pain or Discomfort**: Signs of pain, such as limping, difficulty moving, or vocalizing when touched.
You should consult a vet if you notice any of these symptoms, especially if they persist for more than a day or worsen over time. Early intervention can help address potential health issues before they become more serious.