In infants, what is a common indicator of iron deficiency anemia?

Pale skin is a common indicator of iron deficiency anemia in infants due to the role of iron in producing hemoglobin, the protein in red blood cells that carries oxygen. When an infant is deficient in iron, it can lead to a reduction in hemoglobin levels, resulting in a lower oxygen-carrying capacity of the blood. This insufficient oxygen can cause the skin to appear pale or even have a yellowish tint, as the number of red blood cells diminishes and the overall distribution of blood color in the skin is affected.

In contrast, symptoms like rapid weight gain, hyperactivity, or frequent infections are not directly linked to iron deficiency anemia. Rapid weight gain could indicate overfeeding or other metabolic issues rather than anemia. Hyperactivity can have various causes, including behavioral or developmental factors and is not indicative of iron deficiency. Frequent infections might suggest a compromised immune system or another underlying issue but are also not specifically associated with iron deficiency anemia. Thus, the presentation of pale skin is the most direct and commonly observed sign of iron deficiency in infants.