An infant presents with lethargy and poor feeding. What is a potential cause?

Lethargy and poor feeding in an infant can be indicative of a serious underlying condition, and dehydration is indeed a potential cause. Infants are particularly susceptible to dehydration because they have a higher body water content compared to adults and can lose fluids rapidly. Factors contributing to dehydration in infants include inadequate fluid intake, increased fluid loss due to fever, vomiting, diarrhea, or excessive sweating.

When an infant displays signs of lethargy, it often means that their body is not receiving enough fluids and nutrients to function effectively, leading to decreased energy levels and impaired ability to feed. In severe cases, dehydration can lead to serious complications, including electrolyte imbalances and shock, which require immediate medical attention.

The other options, while relevant to an infant's health, do not typically present with lethargy and poor feeding as primary symptoms. Teething is a common process but usually causes irritation rather than significant lethargy. A common cold primarily leads to respiratory symptoms without severe lethargy or poor feeding. An ear infection may cause discomfort and fussiness, but it is less likely to result in lethargy unless the infection is more severe or associated with systemic illness.