Muslin cotton is the most breathable pick for baby clothes because its open, loose weave lets air move through and lets moisture escape fast. Bamboo and jersey cotton feel soft too, but fleece traps heat and only suits cold weather. For warm days, a double-layer muslin cotton piece that arrives pre-washed soft is hard to beat. Muslin can feel gentle on sensitive skin for everyday comfort; follow your doctor or paediatrician for any diagnosed skin condition.
Parents often ask which fabric actually keeps a baby comfortable in the heat, so here is an honest take on how the main options compare. Muslin cotton is woven loosely on purpose, and those small gaps are exactly what let air move and sweat dry quickly. Bamboo and fleece both have their place, just not the same one as muslin.